This book does a spectacular job of covering the many automatic cannon designs from the late 1800s up to current types. And as the title suggests, it also covers the ammunition associated with these designs.

This is the latest book from Anthony G. Williams, joining previous titles about aircraft guns, (The Flying Guns trilogy, now out of print), sub-machine guns, machine guns, and assault rifles (these three co-authored with Maxim Popenker), and Rapid Fire, an earlier version of the current Autocannon title.

Following the usual introduction, the book is broken down into four main parts, beginning with Part I: A Brief History of Automatic Cannon. This looks back as far as the 1880s for the Maxim designed Ordnance QF (Quick Firing) 1 Pounder, Mk 1, often called the Pom-Pom. Subjects covered include naval anti-aircraft guns, land-based AA, and aircraft-mounted cannon. These topics are arranged in chronological order, ending with modern systems like the naval CWIS (Close In Weapon System) and helicopter gunships.

Part II: Design Considerations introduces us to the finer points of ammunition design. Various types of armor piercing projectiles, explosive and incendiary shells, and fuses are covered. Propellants, primers, and cartridge cases are discussed in much detail. Internal, external, and terminal ballistics are also dealt with.

A subsection of Part II is titled Gun Elements. This looks at various locking systems that have been employed through the years. This is quite technical in nature, but Williams keeps it readable. Also covered in detail (13 pages worth) is the topic of feed systems. From the simple gravity feed of 40mm Bofors guns, through to really large box magazines for 20mm guns, and belt-fed designs as found on various aircraft, this book offers information that is difficult to find elsewhere.

Another subsection of Part II is titled Unconventional Systems. This deals with weird experimental guns and ammunition. Numerous attempts at “telescoped” ammo have been tried, but most go nowhere. Telescoped refers to the projectile being positioned within the case and powder so that it does not extend forward of the case. The British-French 40 x 255mm CTAS (Cased Telescoped Armament System) is finally being delivered to British and French forces. The program started in 1994.

Other experimental ammo types covered include caseless types, the unique “Tround”, and recoilless types.

Part III: The Cartridges is my personal favorite section, and will, no doubt, appeal to any avid cartridge collector. There are an amazing number of cartridges featured here. Every known round from 20mm to 57mm that was used in an automatic gun is listed. This includes both those that saw service, and obscure experimental ones, also. Of course, those obscure ones don’t get as much ink as successful multinational types, as expected. The group photos for 20mm cartridges show 21 service rounds and another 17 experimental types. To keep the chapter manageable, it is subdivided into 20mm, 22-28mm, 30mm, 33-37mm, and 40-57mm cartridges. (Apparently, there are no 21mm, 29mm, etc., hence the number gaps.) Part III runs 61 pages in length.

Part IV: The Cannon is arranged alphabetically, by country. (There is no letter S after the word cannon, as cannon applies to single or plural guns) The USA has a full 38 pages of text and photos, with Russia/USSR having 26 pages of coverage.

The new XM913 Bushmaster III in 50 x 228mm from Northrop Grumman is discussed, indicating this book is right up to date. If adopted, the XM913 is planned to arm the Next Generation Combat Vehicle.

This is a brilliantly researched reference source. It includes data on approximately 200 different cartridges, 400 cannon, and has nearly 500 illustrations.

Anthony G. Williams is primarily an ammunition specialist, but also has an interest in guns. He was the editor of The Cartridge Researcher, the journal of the European Cartridge Research Association, for over fifteen years. He was also an editor of Jane’s Weapons: Ammunition for thirteen years and he maintains a military gun and ammunition website at quarryhs.co.uk.

SPECIFICATIONS

Combat experience in Afghanistan has prompted some rapid changes in the small arms carried by ISAF foot soldiers; and most especially by the U.S. Army, USMC and the British Army and Royal Marines. The purpose of this article is to outline these changes, determine the lessons learned, and look ahead to examine the extent to which the growing variety of rifles including DMRs (Designated Marksman Rifles), carbines, IARs (Infantry Automatic Rifles) and LMGs (light machine guns) might be replaced in the future by a smaller number of weapons without losing any capability.

Developments to Date

Before the Afghan conflict began, it was assumed that most small-arms engagements would continue to take place within the traditional 300 meter limit, as they had in Iraq, and ISAF forces were equipped accordingly. The rifles and LMGs carried by the infantry on foot patrols were overwhelmingly in the relatively short-range 5.56mm caliber, using the NATO standard SS109/M855 ammunition. The U.S. forces used three principal weapons: the M16 rifle (favoured by the USMC), short-barrelled M4 Carbine (favoured by the U.S. Army because its compactness makes it more suitable for urban fighting, the typical scenario in Iraq) and the M249 development of the FN Minimi LMG. Some long-range weapons in 7.62×51 NATO caliber, most notably the M240 GPMG (FN MAG variant) and also some sniper rifles and DMRs, were available for use in a support role when required. The British patrols used the 5.56mm L85A2 rifle, L86A2 Light Support Weapon (effectively an IAR) and the L110 LMG (FN Minimi Para). The L85A2 and L86A2 are the principal members of the SA80 family, which has had a controversial history. As with the U.S. forces, the 7.62mm L7 GPMG (FN MAG) was available in support, and bolt-action 7.62mm sniper rifles were also in service.

These arrangements were thrown into disarray when faced with the very different circumstances of Afghanistan, where the Taliban noted the range limitation of the 5.56mm weapons and, wherever circumstances permitted, opted to engage ISAF troops from longer distances. They could do this because as well as the ubiquitous but short-ranged AK family of assault rifles in 7.62×39 caliber, they have weapons chambered in the powerful Russian 7.62x54R round, equivalent in performance to the NATO 7.62×51. The principal weapons using this cartridge are the lightweight PKM belt-fed LMG and the SVD semiautomatic sniper rifle. Both the U.S. and British forces have reported that more than half of Taliban small-arms attacks are launched from ranges greater than 300 meters, out to as far as 900 meters. While the 5.56mm NATO weapons were previously claimed to be effective out to 450-600 meters, experience has shown that their performance falls off sharply beyond 300m – or even less, when used in short-barrelled weapons.

The adoption by U.S. forces of replacements for the M855, in the form of the M855A1 EPR (U.S. Army) and MK318 Mod 0 (USMC), should resolve some other problems with the existing 5.56mm ammunition concerning erratic terminal effectiveness and poor barrier penetration. However, these are unlikely to help the UK and other NATO nations whose lawyers tend to adopt a very literal interpretation of the Hague Convention prohibition of bullets “with a hard envelope which does not entirely cover the core” – which describes both of the new U.S. bullets. In any case, no 5.56mm developments could achieve enough of an improvement to eliminate the need for a larger caliber to cover the longer small-arms ranges.

The immediate – and indeed, only immediately available – response of the U.S. and UK forces was to redistribute existing 7.62mm weapons to the foot patrols, despite their unsuitability in terms of weight (FN MAG) or low rate of fire (bolt-action sniper rifles). The next stage was to launch urgent requirements for new 7.62mm weapons. In machine guns, both the USA and UK have been developing lightened versions of the FN MAG and also adopting new lightweight MGs, comparable in weight and performance to the Taliban’s PKM. The U.S. already has the MK48, the 7.62mm version of the FN Minimi which the British also selected in mid-2011.

New rifles have been acquired; the U.S. had the advantage of already having selected the 7.62mm M110 SASS (Semi-Automatic Sniper System) and has also refurbished some 5,000 of the old 7.62mm M14 rifles as the M14 EBR (Enhanced Battle Rifle) with modern furniture and accessories. These are proving very popular. The British have acquired a limited quantity of a 7.62mm self-loading sharpshooter rifle from the USA, the L129A1, which is also very popular. In contrast, the USMC has kept one eye on the needs of urban fighting and has rather controversially acquired a new, compact 5.56mm IAR to replace many of the M249s at section level; the HK 416-based M27.

The Case for Change

So we now have the following rifles and MGs in service or in prospect, all intended to be carried by dismounted soldiers on patrol: In the USA, the 5.56mm M4, M16, M27 and M249, plus the 7.62mm M14EBR, M110, MK48 and lightweight M240. That’s a total of eight weapons, four in each caliber. In addition they have heavier support weapons and bolt-action sniper rifles, plus Special Forces use the MK12 5.56mm and the MK17 (FN SCAR-H) 7.62mm rifles.

The UK forces have the 5.56mm L85A2, L86A2 and L110, plus the 7.62mm L129A1, L7 GPMG, and 7.62mm FN Minimi: a total of six weapons, with three in each caliber. Again, there are bolt-action sniper rifles in use as well as these, and special forces use other rifles in 5.56mm and 7.62mm calibers.

Such a variety of weapons has obvious disadvantages in complicating and increasing the cost of acquisition, logistics, maintenance and training. Less obviously, there may also be penalties in combat. Those troops armed with 7.62mm weapons will be penalised by the weight of the guns and particularly the ammunition (7.62mm cartridges weigh twice as much as 5.56mm), plus the much heavier recoil in rifles which slows down aimed semi-auto fire and makes automatic fire impractical. The bigger and less wieldy weapons are also less suited to urban fighting. On the other hand, those with 5.56mm weapons will be able to make little or no contribution to long-range engagements – not even in supplying their ammunition to other members of their section. When combat ranges may fluctuate rapidly it is necessary to carry weapons in both calibres to cover the tactical demands but this reduces the potential firepower of a section in both short-range and long-range engagements.

The urgent need to plug gaps in weapon capability has made the current proliferation of firearms inevitable for the time being, but this situation raises an obvious issue: when planning the next generation of weapons, is it possible to provide a similar range of capabilities with a smaller number of guns, each effective at all normal small-arms ranges?

The key question is: what capabilities do we need from infantry rifles and portable MGs? The answer to this will determine the characteristics of the ammunition, the guns and the weapon sights. These characteristics will also be influenced by new developments in all three fields.

I suggest that the following capabilities should be sought in new small arms, beyond the obvious ones of reliability, robustness, reliability, good ergonomics, reliability, easy maintenance, reliability, ability to accept a wide range of accessories, and of course reliability in extended combat conditions:

1. The rifle should be effective out to the maximum feasible range for small-arms engagements; at least 800 meters. The definition of effectiveness to include hit probability, barrier penetration and rapid incapacitation of personnel.
2. The rifle should be as compact as possible, so that it is handy for urban warfare and for carrying in cramped vehicles and helos.
3. The rifle’s recoil should be light enough to facilitate training, rapid and accurate semiautomatic fire, and controllable burst fire.
4. The rifle should be capable of maintaining a high rate of fire for several minutes.
5. The LMG should use the same ammunition as the rifle, be belt-fed and be capable of accurate and sustained automatic fire out to at least 1,000 meters.
6. The guns and their ammunition should be as light as they can be without compromising any of the above requirements. I will now consider the three elements – ammunition, guns and sights – to examine the implications of these requirements.
   
   Ammunition
   
   In this section I will be considering ammunition performance; essentially, ballistics. I don’t intend to consider advanced cartridge technologies such as the caseless-telescoped and plastic-cased-telescoped rounds being developed as a part of the U.S. Lightweight Small Arms Technologies programme. If one of these is eventually selected for production, it will bring the considerable benefits of a substantial weight reduction, but it won’t alter such matters as the choice of caliber, bullet weight and type, external and terminal ballistics.
   
   To summarise a complex argument: it is both possible and desirable to develop one round which could replace both the 5.56mm and the 7.62mm in portable infantry guns. This would halve the number of different weapons and would also ensure that each weapon has a much wider range of capabilities. It would significantly reduce the weight and recoil compared with 7.62mm ammunition, while improving the range, barrier penetration and terminal effectiveness compared with 5.56mm.
   
   If the ammunition is to be effective at long range, it must match the standard 7.62mm NATO ball round in its trajectory, retained energy and barrier penetration at 1,000 meters from the same length barrels. However, if it is to reduce the ammunition weight and recoil compared with 7.62mm, it must be smaller and less powerful. This conflict can be resolved by selecting a caliber intermediate between the 5.56mm and 7.62mm, with a low-drag bullet which will lose velocity (and therefore energy) more slowly than the 7.62mm ball. Other things being equal, low-drag bullets are heavier than usual, so to keep recoil in check need to be fired at a lower velocity. Muzzle energy will be lower than the 7.62mm (but appreciably higher than the 5.56mm) but the right specification of low-drag bullet will eventually catch up with and even surpass the 7.62mm at long range.
   
   In practical terms, the smallest caliber likely to deliver a performance comparable with the 7.62mm is 6.5mm, while the largest which would enable recoil and weight to be kept in check is 7mm. Exactly which caliber proves to be the best compromise should be determined by more detailed analysis, comprehensive testing and preferably combat experience. Initial calculations indicate that a muzzle energy in the region of 1,800-1,900 ft/lbs will be required, compared with figures of around 1,250 ft/lbs for the 5.56mm and 2,500 ft/lbs for the 7.62mm. Experience of existing cartridges in this class indicates that the weight will be mid-way between the 5.56mm and 7.62mm, but the perceived recoil will be much closer to 5.56mm, thereby maintaining good controllability.
   
   The U.S. Army’s ARDEC Small Caliber Munitions Technology Branch recently conducted an analysis of calibers for future infantry weapons, with the results emerging in March 2011. A wide range of criteria were examined including: penetration; terminal effectiveness; accuracy; initial, retained and striking energy; wind drift; stowed kills; and recoil. The existing 5.56mm and 7.62mm rounds were tested at various ranges in comparison with 6.5mm and 7mm, in all cases when loaded with similar lead-free bullets (copper or copper+steel – the latter representative of the M855A1). The conclusion of the study confirmed that calibers in the 6.5mm to 7.0mm range deliver the optimum characteristics for use in military small arms. This issue has since been followed up by a Joint Caliber Working Group sponsored by the TSWG Tactical Operations Support Subgroup.
   
   Gun Design
   
   The need for good long-range performance combined with a short overall length for handiness in urban fighting and in vehicles causes problems for traditional rifles, since the first requires a long barrel and the second a short one. A folding stock can resolve the carrying problem (where that is possible: which it isn’t with the M16 and M4, for instance, as the action extends into the stock) but doesn’t help in urban fighting when the stock must be extended to provide controllability.
   
   One option is to have barrels of different lengths which can be changed depending on the circumstances, but that may not be convenient, particularly if the ranges keep changing during a patrol (for example, a section might be searching a village but then be attacked from long range as they leave). Another option is to select a compromise barrel length, but this will result in a gun which is longer than is desirable in urban fighting and which will have a reduced long-range performance – unless the power of the cartridge is increased to deliver the same performance from a shorter barrel, in which case the ammunition weight, recoil, muzzle flash and blast will be increased. The obvious solution to this dilemma is to adopt a bullpup configuration, with the action and magazine located at the back of the gun, behind the pistol grip.
   
   The proposal of a bullpup is controversial since the U.S. Army has never used them, while the British Army has been put off them by the long and painful saga of the SA80, so requires some further justification.
   
   There are three principal objections to a bullpup:
   
   1. Poor ergonomics: the location of the action and magazine well to the rear of the pistol grip makes operating the controls and changing magazines more difficult. This is particularly an issue with the SA80.
   
   2. Lack of ambidexterity: most bullpups (although not the SA80) can be converted to left-hand use, but that takes some time to achieve so can’t be done in the heat of battle. This means that users can’t switch shoulders to aim round the corner of a building, for instance, without being hit in the face by their own ejected cases.
   
   3. Lack of ability to adjust the stock length to allow for the wearing of body armour: again, a particular problem with the SA80 which has quite a long stock.
   
   Apart from these practical concerns, some users dislike the rearward weight balance of the bullpup and the proximity of the action to the firer’s head in case of a chamber explosion.
   
   There are responses to all of these objections:
   
   1. The ergonomics do not have to be as poor as the SA80’s: the latest version of the Israeli Tavor, for instance, has controls which match those of the M16 and M4 in location and operation, since it was designed to replace them.
   
   2. There are various ways of achieving ambidexterity. The FN F2000 uses a forward ejection tube, which carries the spent cases to the front of the gun before they are expelled. The new Beretta ARX-160, although not a bullpup, has a mechanism which changes the case ejection side at the flick of a switch. The STK SAR-21 from Singapore has a simpler solution for emergency left-hand use: a large and effective case deflector.
   
   3. An adjustable stock could be provided if the gun action behind the magazine were designed to be shorter: something which hasn’t happened so far since there has been no call for it. However, that should not be difficult to achieve in a new design.
   
   Gun balance is, to a great extent, a matter of what you are used to. Some bullpup users prefer the rearwards weight balance, arguing that it is easier to hold one-handed or for extended periods, and makes the rifle quicker to change aim. What is undoubtedly true is that a bullpup is far more evenly balanced once an under-barrel grenade launcher, large electro-optical sights and other tactical kit (e.g. torches) start being added: a traditional rifle then becomes massively front-heavy.
   
   The firer’s head can be shielded from the action by using a tough Kevlar cheek-piece, as with the STK SAR-21; this could be designed to flip quickly from one side to the other in conjunction with a switchable-side ejection system like the ARX-160’s.
   
   It is worth emphasising the key argument in favour of the bullpup: the design reduces the overall gun length by some eight inches for the same barrel length, which is a huge reduction. This is not just an advantage in urban fighting; it also facilitates fitting a suppressor, which is increasingly popular to reduce muzzle blast and flash and make firers more difficult to locate (it also protects the firer from long-term hearing damage). With barrels of the same length, a bullpup with a suppressor will be about the same total length as a traditional rifle without one.
   
   In addition, the adoption of a general-purpose intermediate round as proposed here would strengthen the case for the bullpup. At the moment, it is possible to argue that 5.56mm rifles can have short barrels because they are now principally seen as short-range weapons. On the other hand, 7.62mm rifles are being introduced for the long-range role and therefore don’t need to be very compact for urban warfare. However, a single general-purpose infantry rifle in a general-purpose caliber must be well suited to both urban fighting and the long-range role. As previously mentioned, this combination can be achieved with a modular traditional design with quick-change barrels of different lengths (as most recent designs offer), especially if the action design also allows the stock to be fully telescoped. However, the bullpup layout does not require any such changes, and it is effectively two existing weapons – a rifle and a carbine – in one.
   
   One issue which often receives little attention is recoil control, which as already observed is important in a rifle in order to facilitate training, rapid and accurate semiautomatic fire and controllable automatic fire. In guns of similar type, recoil is largely a function of the gun weight and the cartridge power (specifically, the momentum – mass times velocity – as opposed to energy – mass times velocity squared). However, the gun action can also have a significant effect, with advantages being demonstrated by soft-recoil mechanisms or even opposed-piston types like the AK-107. The U.S. Army has recently been researching this and achieved reductions in the peak recoil force of up to 90% by using a counter-mass principle; but this would inevitably add weight. Controllability in automatic fire can also be enhanced simply by reducing the rate of fire. The very high cyclic rate common in modern 5.56mm small arms has little if any practical benefit and leads to more rapid ammunition exhaustion and barrel heating as well as greater cumulative recoil.
   
   To achieve a large volume of automatic fire, as may be involved in fighting off a close-range attack, usually requires a heavier barrel to delay overheating. However, the U.S. HPAWA project (High Performance Alloys for Weapon Applications) aims to result in barrels which will withstand far heavier rates of sustained fire, so that MGs can be issued with only one barrel. Good progress has since been reported by ARDEC in the development of highly temperature-resistant cobalt alloys. If such alloys reach production, this should enable a standard rifle to offer volumes of fire comparable with an IAR without any increase in barrel weight. The problem of cook-off after an intense engagement could be addressed, if need be, by arranging for the gun to fire from an open bolt in automatic mode (although the USMC has not required this of their new IAR). In other words, we could replace three weapons (carbine, rifle and IAR) with one.
   
   The design of the belt-fed LMG to accompany this rifle has not been discussed here, since the same design problems do not apply and existing designs could be adapted well enough to a new cartridge. The adoption of a general-purpose intermediate cartridge developing significantly less recoil than the 7.62mm would however obviously allow the weight of the gun to be reduced without compromising reliability, which with the significantly lighter ammunition would deliver a substantial reduction in the weight currently carried by GPMG gunners and ammunition carriers.
   
   Sights
   
   Rifle and MG sights are currently making great advances in capability. Variable magnification has been available on the specialist market for a very long time, and has now been joined by dual-magnification military sights, initially from Elcan (with 1-4x and 1.5-6x versions currently available), equipping the infantry with a sight suitable for both short and long-range use. The addition of electronics is bringing even more dramatic advances, most obviously in night-vision capability. In 2010, the U.S. military stated a requirement for a 1-4x day/night sight, merging thermal and light intensifying images, with a built-in rangefinder (and possibly a laser pointer), with a 3 lb (1.36 kg) weight, low power consumption and a price of $3-5,000. With this kind of technology, such issues as air pressure, weapon cant and the effects of firing up or down hill can also be taken into account in providing an aiming solution.
   
   Even more remarkable is the LIDAR (Laser Identification Detection And Ranging) unit developed by the Israeli Soreq Nuclear Research Center. This works by firing a laser beam at the target, the reflection being captured by an array of photodiodes. Fluctuations in the signals received by the photodiodes are used to detect the direction and velocity of any cross wind, which can have a major effect on hit probability at long range. Something like this may well have an application in the DARPA One Shot next-generation sniper scope programme. The One Shot programme is intended to enable snipers to be on target with the first round, under crosswind conditions, up to the maximum effective range of the weapon: a target of 65% probability of a first-round hit at up to 1,500 meters has been set when using long-range sniper rifles.
   
   What all of this means is that we are soon likely to see practical day/night variable magnification sights which can take into account all of the usual factors which affect bullet trajectory. All the soldier will have to do is to lase the target and the sights will automatically indicate the correct aiming mark to put the bullets into the target area.
   
   Initially, such sights will be bulky, heavy and expensive and thereby restricted to snipers, but it is safe to predict that within the foreseeable future they will become smaller, lighter and eventually cheap enough for general issue. This is enormously important because it means that the main objection to providing rifles with a long-range capability – that most soldiers will never be well-enough trained to hit anything at such ranges – is removed. In conjunction with a long-barrelled standard rifle and long-range intermediate ammunition (and assuming a fundamentally accurate weapon and good-quality ammunition production), this also means that a separate DMR or sharpshooter rifle may no longer be required. Potentially we could therefore replace four existing guns (carbine, rifle, IAR, DMR) with one.
   
   The same sights and ammunition will of course also transform the long-range effectiveness of the belt-fed LMG, although the sustained-fire capability of a rifle with an advanced-alloy barrel may mean that fewer MGs will be needed.
   
   Conclusion
   
   So we have reduced our two cartridges to one, and our six or eight different guns to two – the general-purpose infantry rifle and the belt-fed LMG – without any loss in capability. The practical and financial advantages of such a simplification would be huge, as would the boost to the capability of the infantry sections in whatever tactical circumstances may arise.
   
   Various attempts have of course been made to introduce an intermediate round before, one of the first being the .276 Pedersen of the late 1920s. After exhaustive tests this was recommended for adoption by the U.S. Army and the British were also very interested, but it was cancelled principally for financial reasons. The modern equivalent is the 7×46 UIAC (Universal Infantry Assault Cartridge), an experimental round being developed by Cris Murray who was involved in the development of the 6.8mm Remington SPC.
   
   All of the technologies which I have mentioned are either available now or are very likely to be available by the time the next generation of small arms has been developed.
   
   If LSAT succeeds (and the plastic-cased telescoped version is currently looking promising), then a dramatic weight reduction can be added to the other advantages; it would mean that an LSAT intermediate round could weigh about the same as the current 5.56mm.
   
   Now all we need is the people in the right places with the vision to see and drive towards what is possible, rather than simply going down the same old road because that’s what we’ve always done. It is time for small arms to leave the 20th century.

This article first appeared in Small Arms Review V16N1 (March 2012)

The story of the .50 Browning in World War 2 is well known; its extensive use by U.S. and subsequently Allied forces on land, sea and in the air established its reputation and usefulness to such an effect that it remains a valuable weapon today. Comparable weapons were fielded by Soviet forces in 12.7×108 caliber, which also still survives in service to this day in several different guns. However, the Browning was not the only gun to be designated .5 inch to see service during that conflict: the British had their own version using unique ammunition; the .5 inch Vickers.

The story of the Vickers gun is also well known. It originated in the first successful self-powered machine gun, the Maxim of 1884, which had become the standard machine gun of the British Army by 1891 and was adopted (under various names) by many other nations. A modified version with a more compact mechanism was adopted by the British Army early in the 20th Century as the Vickers-Maxim but later simply became known as the Vickers gun. It was available for various rifle cartridges up to .45 inch but in British service was overwhelmingly used in .303 inch caliber. It fought through two world wars and remained in front-line British service until the mid-1950s. The .5 inch version had a much shorter life, emerging in the 1920s and disappearing from view after World War 2.

Ammunition Development

The origin of the .5 inch Vickers goes back to the First World War, when a need arose for a larger-caliber machine gun for several different reasons. One was the need to fire bullets large enough to carry a useful incendiary charge to set light to enemy hydrogen-filled balloons and airships. To achieve this, some of the rifle-caliber Vickers had been chambered for obsolete rifle cartridges such as the 11mm Gras (tested by the U.S. into the 1920s), but a purpose-designed modern cartridge would obviously be better. The second was the need for a more hard-hitting machine gun against aircraft, some of which were now being fitted with armor. The third was the development of the tank, which required a better armor-piercing performance than rifle-caliber guns could achieve.

The initial British developments during the Great War were based around a .600/.500 inch cartridge originally derived from an elephant gun round. This first appeared in an anti-tank rifle, the Godsal of 1918, followed by a slightly scaled-up Vickers. The Godsal was never adopted (although one example has survived) but the cartridge for the machine gun went through various evolutions, included a version with a belted case, until the final form emerged in 1921. This used a rimless 12.7×81 case and was known by Vickers as the .5V/580, after the bullet weight in grains. The exact bullet diameter was fractionally greater than the contemporary .50 Browning’s, at 0.514 inches compared with 0.510 inches. Muzzle velocity was around 2,460 fps and total cartridge weight 1,280 grains. It developed about three times the muzzle energy of the .303 inch, but only two-thirds that of the .50 Browning.

The ammunition was officially adopted for service in 1924.

Several different loadings of the .5V/580 round were developed for British service including Ball (with a two-part core: lead in the base and aluminium in the tip), Armor Piercing (with a hardened steel core), Semi-AP (with an unhardened steel core), SAP-Tracer, and Incendiary (which was similar in design to the U.S. .50 incendiary). The ones most commonly used in service were the SAP and SAP-T, because their penetration wasn’t much less than the AP and they were a lot cheaper.

All of the bullets in British service were flat-based, which limited their maximum ballistic range to 4,265 yards. They could achieve a maximum altitude of 9,500 feet. Of course, the effective ranges were very much less than this; they were probably in the region of 800 yards against aircraft and 1,600 yards against small surface targets.

The British Guns and the Browning Tests

The Vickers .5 inch gun developed to fire this ammunition was offered in three different versions for the three services. The army gun was water-cooled and initially fired at 450 rpm. The naval version was similar in appearance but had the rate of fire boosted to 700 rpm by the removal of the delay pawl which held the crank until the barrel returned to battery – stronger buffer springs were also fitted. The air force version combined the 700 rpm rate of fire with an air-cooled barrel. The army and naval versions had the traditional large-diameter fluted water-cooling jacket, just like the rifle-caliber version, with the naval gun distinguished by a very long flash-hider, but the aircraft gun looked radically different, with flat, tapered plates running each side of the barrel. Barrel lengths were 31 inches or 62 calibers, overall lengths 47-53 inches. The gun barrel recoiled a maximum of 1.25 inches and a recoil pull of 385 lbs was developed. The guns were belt-fed, using either a web belt (initially) or a disintegrating steel link type, with 100 rounds in the belt.

During the 1920s the British Admiralty tested an early .5 inch Vickers in comparison with the M1924 water-cooled version of the .5 inch Browning gun. A 1928 report of the tests has survived and Chart 1 reveals this information.

• Mechanisms: Vickers rated superior, as consists of only two parts (lock and feed box) compared with three (bolt, feed box and recoil buffer). The Vickers lock takes only one-third the time to replace, the feed box is also quicker to replace as well as being more reliable, and the feed being driven by gun recoil has no ill effect on the operation of the lock.
• Rate of Fire: both can be adjusted up to 750 rpm, but the Vickers can be adjusted by means of a crank check lever which can be regulated during firing, while the Browning requires the back plate to be removed to adjust the recoil buffer.
• Temperature: the much larger water capacity of the Browning kept the barrel cooler, as shown in Chart 2.
• Choking of Barrel (i.e. fouling by bullet jacket deposits): slightly greater in the Vickers due partly to higher barrel temperatures and partly to a difference in hardness in the bullet casing (jacket). It was noted that this was less with AP bullets
• Fouling and grit: both guns performed satisfactorily, but it was noted that the Browning ended up with more grit in the mechanism due to it being more exposed by the opening of the gun casing. Also, after prolonged gun firing the Browning’s mechanism was coated with black fouling while the Vickers’ was clean.
• Control: in both guns, the vibration was too severe to keep them on target so shoulder stocks were recommended for accuracy.
• Belts and filling machines: neither web belt was found to be satisfactory. The Vickers belt was made using metal spacing strips and eyelets, which were inadequately secured, while the Browning’s was stitched and could only be used two or three times. Both metal link belts were satisfactory. The Browning had filling machines for both types of belt (the metal belt filler was commended, the web one condemned), the Vickers had none.
• Reliability: it was noted that the Vickers was an early example and suffered some problems, but these were corrected with modified parts during the trials and it was then very reliable. The Browning was reliable at high rates of fire but less so at lower rates, especially at higher elevations. Any kink in the belt would cause a failure to feed. The Browning’s casing fractured during the test.
• Conclusion (reproduced in full): “The results of the trials lead to the conclusion that the .5-inch Vickers has the following advantages:

1. Greater reliability
2. Wear and failure of parts – if any – are to minor parts that can be readily replaced.
3. Care and maintenance is easier to the inexpert, on account of its less complicated recoil and buffer mechanisms.
4. The mechanism and functioning of the gun requires less special or expert knowledge to obtain a good, reliable performance, and is more readily understood by the average seaman, who already receives training in the similar mechanism of the .303-inch gun.
5. Readily converted to right or left gun.
6. From a general technical point of view, it is the opinion that the fundamental principle of the mechanism and the action of the Vickers gun is superior to that of the Browning, and is more certain in its action generally.

The .5-inch Vickers gun is therefore recommended for the Naval service in preference to the Browning gun.”

The Aircraft Guns

The RAF also evaluated the .5 inch Vickers and Browning guns. The results were inconclusive; the Browning was more powerful but was longer and heavier. It was concluded that the .303 inch version of the Vickers was almost as effective as the HMGs against the light, unarmored aircraft structures of the time and it was much lighter as well as faster-firing. The RAF accordingly decided not to proceed with a heavy machine gun, while noting that any widespread adoption of armor for military aircraft would force a re-think. By the mid-1930s, when the increasing performance and toughness of aircraft began to cast doubt on the future of rifle-caliber guns, the RAF opted for the greater destructive power of a 20mm cannon, choosing the French Hispano HS 404. A few .5 inch Browning M2 guns were used late in the Second World War in applications for which the Hispano was considered too big and heavy, but apart from this no heavy machine guns were fitted to British aircraft.

The Vickers wasn’t the only .5 inch gun considered by the RAF. BSA (Birmingham Small Arms) offered their Model 1924 gun for aircraft observers. It was intended to be flexibly mounted so used a long-recoil mechanism to soften the recoil kick, and was fed by a pan magazine on top of the gun. Initially, this used BSA’s own (very similar) ammunition but it was later slightly modified to use the Vickers 12.7×81 cartridge. The RAF rejected it as being too heavy, too slow-firing (only about 400 rpm) and having too small an ammunition capacity (37 rounds).

The Naval Guns

The naval version of the Vickers .5 inch, designated the Mark III, was the most successful, with over 12,500 accepted for service in the Royal Navy. It was initially used in a curious four-barrel mounting in which the guns were stacked vertically, which in 1939 was the RN’s standard short-range AA equipment. This was manually-operated, but later in the war a power-operated twin mounting (with side-by-side guns) was used in motor gun boats and similar craft. As an AA gun it soon proved insufficiently powerful and was gradually replaced during the war by the 20mm Oerlikon. China bought 19 examples of this gun.

The four-barrel mounting had its guns adjusted to provide a spread of fire, amounting to 60 feet wide and 50 feet high at 1,000 yards. The belts were wrapped around large drums which carried 200 rounds per gun. Vickers claimed that it could fire all 800 rounds in 20 seconds and could then be reloaded in a further 30 seconds. They also claimed, rather optimistically, that it “could deal with aircraft at ranges of 1,500 yards and below.”

A specification document dated November 1935 exists concerning the supply of “Vickers 12.7mm Automatic Gun Mark III (Amended)” for installation in submarines of the Turkish Navy, but it is uncertain whether these weapons were actually delivered or used. The rate of fire in this example is quoted as 600 rpm, with AP or SAP ammunition being specified. Some details of the performance guarantees are summarised below:

• Accuracy: when fired from a fixed (test) barrel, the average size of a 20-round group must not exceed 12 inches at 500 yards.
• Armor penetration: 70% of rounds fired must perforate a 15-16 mm hard steel plate (440-480 Brinell) at 100 yards, normal impact. Perforation will be considered to have occurred when (a) daylight is visible through the plate, or (b) when the core, being left in the plate, projects beyond the back surface of the plate.

The Army Guns

The British Army only officially used its .5 inch Vickers in armoured vehicle turrets. The initial model was designated .5 inch Mark I but improvements were made before this was issued as the Mk II. Later, the Mk IV was introduced which had the same mounting dovetail as the .303 inch gun and had its rate of fire increased from 450 to 600 rpm. The Mark V was the final AFV version, improved and strengthened, and over 1,000 of these were made by 1940 (only just over 100 of the earlier models being manufactured).

The Infantry Tank Mk 1 was equipped with one of these guns in a one-man turret, but apart from this the .5 inch was usually paired with a .303 inch Vickers in armored cars and light tanks. Some units of the Long Range Desert Group “acquired” these guns and fitted them to pintle mountings on their 4×4 vehicles. They usually lack the flash hider and can be distinguished from the .303 inch version by the lack of the bulbous muzzle booster in front of the cooling jacket.

Early in the Second World War both Vickers .303 inch and .5 inch guns were replaced in their AFV roles by two guns from Czechoslovakia, the 7.9mm ZB vz/53 and 15mm ZB vz/60. These were both known as “BESAs” in British service.

The Semi Rimmed ‘Export’ Cartridge and its Guns

Vickers may not have had much success in selling their big gun to the RAF but it attracted foreign interest. The British Government didn’t like Vickers selling their latest equipment abroad so Vickers slightly modified the cartridge case to make it semi-rimmed, giving the designation 12.7x81SR; this variant being developed as early as 1923. Vickers knew the cartridge as the .5”V/565 as their standard bullet for it weighed 565 grains; it had a muzzle velocity of 2,490 fps. Bullet types developed for this cartridge included Ball, AP, AP-T, Flame Tracer, and Smoke Tracer / Incendiary (similar to the Buckingham type used in the .303 B Mk IV).

Some 65 Vickers aircraft guns in this caliber were bought by Japan and 49 by Siam (Thailand) but it is not clear what service use was made of them.

The Italians used the Vickers cartridge in their own 12.7mm Breda-SAFAT and Scotti aircraft guns. The short-recoil Breda-SAFAT was not a sparkling performer, weighing 64 lbs and firing at 700 rpm, but it was the standard Italian fixed aircraft gun at the start of the Second World War, two synchronised guns normally being mounted in the cowling of single-engined fighters. The gas/blowback Scotti fired no faster, but did weigh only 51 lbs. It seemed to be more highly regarded but was primarily, if not solely, used in flexible mountings. The Italians developed various different loadings for the semi-rimmed cartridge, including Tracer, AP, API, API-T, I-T, and (unusually for an HMG) HE and HEI-T. The HE contained around 12.3 grains of Penthrite wax.

The Italian fighters and their 12.7mm Breda-SAFAT guns were adopted by Spain and Hungary, who made their own ammunition. The Hungarians also used the 12.7x81SR cartridge in the HMG version of their interesting Gebauer GKM engine-driven twin-barrel gun, which was fitted to the Hejja II (licence-built Reggiane Re 2000).

The Japanese Army also became interested in the Breda-SAFAT and in particular its explosive shells, and considered adopting the gun. In the end they did adopt the cartridge but developed their own, superior, aircraft gun, the 12.7mm Ho-103 (based on a smaller version of the .50 Browning) to use it. This fired at 900 rpm and weighed only 48 lbs. It was the standard fighter gun of the Japanese Army Air Force in the latter part of the War. The Japanese also developed their own HE ammunition as well as using the Italian designs.

The Class D

Even less well known is the Vickers .5 inch Class D or HV (for high velocity), also developed in the mid-1920s. This was basically a lengthened version of the usual .5 inch gun, designed around a much bigger and more powerful 12.7x120SR cartridge, initially known as the V/664 (with 664 grain flat-based bullets), which was later replaced as the standard loading by the V/690 (690 grain boat-tailed – streamlined – bullets), which achieved an impressive muzzle velocity of 3,040 fps. Bullet types developed for both the V/664 and V/690 were Ball, AP, AP-T, Flame Tracer, and Smoke Tracer / Incendiary. Weight of the V/690 cartridge was 2,080 grains and a belt of 100 rounds weighed 33.5 lbs. Maximum range claimed was 7,000 yards with a vertical altitude of 15,600 feet but, as with the 12.7×81, effective ranges would have been far less; probably 1,000-1,200 yards in AA fire and double that against ground targets.

The gun barrel was water-cooled as usual and the rate of fire was 350-450 rpm. Gun weight was 101 lbs, or 122 lbs with water, and it was noticeably longer than the compact Class B, with a barrel length of 45 inches and an overall length of nearly six feet. This was offered primarily as an AA gun in a twin mounting, or as an anti-tank gun in a single mounting, although both mountings could be used in either role. The single mounting, complete with water, weighed 623 lbs while the twin weighed just over one ton in action.

Despite various experiments (including installing a twin mounting on a Vickers Light Tank Mk 1A) the Class D was never fielded by Britain. It did achieve some very limited foreign sales; Siam bought 24, China 20 and Japan 48. It is unclear whether any of these saw combat.

Conclusion

The British were never very keen on heavy machine guns, regarding them as being less effective than 20mm cannon firing explosive shells and not really worth the extra size and weight compared with rifle-caliber MGs. As a result, the Vickers .5 inch guns saw relatively little use and their .50 Brownings even less. Ironically, the particular circumstances of recent conflicts have led to the British making more use of HMGs today than they have done at any time since the end of World War 2 – in the shape of the old Browning M2.

The phone call from Carl Bertil Johansson in early summer 2009 came out of the blue. The founder of the Swedish company CBJ Tech had read an article I’d written about military Personal Defence Weapons (PDWs) for soldiers who do not normally carry a rifle. I had concluded that the optimum weapon configuration would be a compact machine pistol like the 9mm Brügger & Thomet MP9. I had also observed that the gun’s ballistics could be transformed by adapting it to fire the 6.5×25 CBJ cartridge. He thought this idea sounded promising so had contacted Brügger & Thomet, who were interested enough to supply him with an MP9 featuring a prototype barrel in 6.5×25 calibre. Initial testing had made him so enthusiastic that he was calling to invite me to Sweden to try the gun and ammunition combination for myself. How could I refuse?

The MP9

The MP9 has been developed from the Steyr Tactical Machine Pistol or TMP, to which Brügger & Thomet acquired the rights in the early 2000s. This innovative Swiss company has made a number of modifications, the most obvious being a side-folding shoulder stock, which transforms the steadiness of aim and the effective range. They have also added a NATO accessory rail on top for optical sights, ghost ring rear sights with an adjustable foresight, a trigger safety (similar to the Glock system), a suppressor attachment on the barrel sleeve (B&T also make the suppressors), and translucent magazines for 15, 20, 25 or 30 rounds. Options include a Picatinny rail under the barrel in lieu of the fixed handgrip, and a fixed skeleton rather than folding stock. The standard colour of the body is black but green and coyote tan are also available, as is a blue version adapted to fire Simunition FX training ammunition (which can also work with the new Force on Force cartridge recently introduced by ATK) and a red “manipulation” gun which cannot fire live ammunition and is used for safe handling training.

The result is an exceptionally compact and lightweight submachine gun or machine pistol, largely made from polymer and weighing just 1.4 kg (3.1 lbs) empty. Loaded 9mm magazines weigh 240 grams (8.5 oz) for 15 rounds to 440 grams (just under 1 lb) for 30 rounds. The MP9 is 303 mm (11.9 inches) long with the stock folded and 523 mm (20.6 inches) with the stock unfolded. Barrel length is 130 mm (5.1 inches). Unlike most SMGs (with the notable exception of the Heckler & Koch MP5 series) the gun fires from a closed and locked bolt, utilising a rotating barrel locking system; it will still fire when the muzzle is pressed against the target. The cyclic rate of fire is 750-800 rpm. The single shot/automatic selector and manual safety switch is a push-button by the thumb.

According to B&T, about 5-6,000 MP9s are sold every year. The gun is widely exported and is now in service with many special forces and close protection teams. The use of the ubiquitous 9mm cartridge is a significant selling point, along with the compact dimensions, the open holster (the gun clips into it) and the availability of the training versions. The modest penetration of 9mm ammunition isn’t felt to be an issue as hardly any of the expected opposition use body armour (this may not, of course, remain the case indefinitely), and around 50m is regarded as an adequate range for its particular role.

The nearest competitor to the MP9 is the Heckler & Koch MP7. The most obvious difference between them is that the MP7 is available only in HK’s unique 4.6×30 calibre, whereas the MP9 fires the 9×19 NATO, aka Parabellum or Luger, which is readily available from many manufacturers in a very wide range of loadings. At least, that was the case until recently, when the first example of the B&T MP9 in the 6.5×25 CBJ version appeared.

The 6.5×25 CBJ

Carl Bertil Johansson is an experienced gun designer who has worked with Aimpoint and SAAB Bofors among others, but set up CBJ Tech to develop his idea for a high-performance cartridge. The company, a family-run business, is based in southern Sweden and owns a Cold War bunker that provides very secure accommodation for workshops and range testing.

CBJ started development of the 6.5×25 cartridge in the late 1990s at the time of the NATO competition to select a new PDW round. This was intended to replace the 9×19 with longer-ranged ammunition able to penetrate NATO’s CRISAT target (equivalent to contemporary Russian body armour) at 150 metres. The only cartridges officially tested were the 5.7×28 FN developed for the P90, and HK’s 4.6×30 for the MP7. It proved impossible to reach political agreement on which to choose, so no decision was made.

FN and HK both started with “clean sheet” ammunition and gun designs, but Carl Bertil decided on a different approach, reasoning that a cartridge that was interchangeable with the universal 9×19 round by means of a simple barrel swap would have a much wider appeal. It would mean that existing guns could be adapted to fire the new cartridge, and also that guns in the new calibre could be easily changed to 9×19 if required; even the magazines remain the same.

This design principle meant that the new CBJ cartridge would have the same overall dimensions as the 9×19 (including the rim diameter) and would need to develop a comparable recoil impulse to ensure reliable gun functioning. The cartridge that emerged from this study was the 6.5×25, with an extended, necked-down case and a short bullet protrusion. Several different loadings in three ballistic groups have been developed.

To compete with the 5.7mm and 4.6mm rounds in meeting the NATO PDW long-range penetration requirement, a sub-calibre loading is used. The standard military “ball” loading is actually a 4mm calibre tungsten bullet in a plastic sabot. The bullet weighs 2 g (31 grains), 2.5 g with its sabot. There is a “spoon-tip” version designed to encourage more rapid bullet upset on impact, and a training variant using cheaper core material. All of these are fired at a muzzle velocity ranging from 730 m/s (2,395 fps) from a 127 mm (5 inch) barrel (the recommended minimum barrel length) to 900 m/s (2,950 fps) from a 305 mm (12 inch) barrel. The tungsten-cored loadings fired from a 12 inch barrel match the trajectory of the 5.56×45 NATO from an M4 Carbine and have much superior penetration to its standard SS109/M855 ammunition, being able to punch through 9mm armour plate. From a 12 inch barrel, velocity at 300 metres is 578 m/s (1,900 fps) at which range it will still penetrate the CRISAT target.

The 6.5mm version of the MP9 has the barrel extended to 150mm (5.9 inches), giving a muzzle velocity of just over 800 m/s (2,620 fps). By comparison, the 5.7×28 P90 and 4.6×30 MP7 both fire as standard 2 gram (31 grain) bullets at about 720 m/s (2,360 fps). A brass-jacketed 6.5mm ball round weighs 7.5 grams (115 grains) compared with 6.2-6.4 grams (96-99 grains) for the 5.7 and 4.6 rounds and around 12-13 grams (185-200 grains) for 9mm. Loaded 15 and 30-round 6.5mm MP9 magazines therefore weigh about 165 and 290 grams (5.8 and 10.2 oz) respectively. Steel and light-alloy cases are being considered by CBJ, but the initial emphasis is on brass.

The other ballistic groups fire full-calibre 6.5mm bullets. One group, primarily intended for police use, fires lightweight 2.5 gram (38.6 grain) bullets at the same velocities as the sub-calibre loadings. These consist of the HET (high energy transfer) brass bullet and a frangible (polymer/metal powder blend) version for use in training or when barrier penetration needs to be minimised. The HET will also penetrate the CRISAT armour target at short range, but these rounds are most effective within 50 metres as the lightweight bullets rapidly lose velocity. The third ballistic group has just one round – subsonic armour piercing – intended for use with a suppressor. It is much heavier than the other bullets at 8 grams (123 grains) and can also penetrate the CRISAT target.

The 6.5×25 cartridge cases were previously made by reforming 9×29 Winchester Magnum brass, but CBJ Tech now has cases specially made for them. These use slightly thicker brass, requiring some adjustment to the propellant loads. The colour of the sabots has not yet been firmed up; originally these were black but this was changed to white to aid recovery from the indoor range’s backstop which has an outer layer of shredded black rubber. For production purposes, different colours may be used to indicate the loading.

SAAB Bofors was initially involved in helping to market the 6.5x25mm while the NATO competition was running, but is no longer involved with the project. CBJ Tech is continuing to develop the ammunition and demonstrate its capability in a wide variety of converted submachine guns and pistols. Those tested to date range from the Steyr AUG SMG to SIG Sauer and Glock pistols. Where necessary, pistols are fitted with barrels extended to 5 inches. A substantial purpose-designed SMG, the CBJ MS, was initially developed to use the new round and features a folding bipod and an optional large-capacity drum magazine in order to act as a light support weapon out to 400m. However, CBJ Tech is now mainly focused on adapting existing 9mm weapons, particularly the MP9 as this is seen as the ideal combination for the PDW role in which there is growing military interest. The remarkable performance of the 6.5mm cartridge, especially in armour penetration, is such that CBJ is intending to offer their conversions only to military and police customers.

How it Works Together: the MP9 in 6.5×25 CBJ

Once in Sweden I had the opportunity to test-fire the MP9 in both 9mm and 6.5mm calibres alongside other weapons for comparison purposes, in two locations; an outdoor range in semiautomatic fire and in CBJ’s indoor range on automatic. Before this, I had only been able to handle the MP9 so I was keen to see how it performed.

In either calibre the MP9 is a pleasure to shoot. I found the spacing between the butt, the pistol grip and the forward handgrip suited me well. The fat, forward-sloping front handgrip greatly aids control and I would certainly not wish to do without it. For semiautomatic fire the little 1.5x Trijicon sight proved ideal and the effective range of the 6.5mm version firing the saboted tungsten ammunition would probably be around 200 metres. In 9mm calibre or for close-range work a 1x holographic red-dot sight (also tried) might be preferred.

Given the MP9’s small size and weight I was surprised by its controllability in automatic fire. As a UK civilian my opportunities for firing automatic weapons are nearly zero but I found no trouble in keeping the rounds on target when firing short bursts; the little gun was much easier to control than an M16 I tried afterwards.

There was very little difference between firing the 9×19 and 6.5×25 versions of the MP9. Subjectively, the 6.5mm version felt as if it had slightly less recoil. My arrival coincided with CBJ’s working up of loads using their new cartridge cases. They hadn’t finalised this process and the 6.5mm version suffered some failures to feed with the new cases (although it performed very well with the older ones) but that was expected to be a temporary glitch.

A key question in my mind was this: OK, the little 4mm tungsten bullet goes through armour like the proverbial hot knife through butter, but how does it perform against unarmoured personnel? This question could only finally be decided in combat, of course, but ballistic gel provides a repeatable substitute for testing purposes. CBJ Tech has the facilities for this, and performed some tests for my benefit. I witnessed three different cartridges being compared at about 5 metres range; the standard 6.5mm saboted ball (this one first had to penetrate a CRISAT target), the full-calibre 6.5mm HET and the 9×19 NATO FMJ. The results are shown in the photograph. The least impressive was the 9mm, while the 6.5mm HET showed far more disruption with rapid bullet upset. The saboted ball also performed significantly better than the 9mm, and according to previous tests I was shown, the spoon-tip version demonstrates even faster upset as one would expect. Interestingly, on one of the test shots of the saboted rounds the sabot was found stuck into the surface of the gel block, which showed that it had followed the bullet down-range quite closely.

To sum up, the Brügger & Thomet MP9 is arguably the best of the new breed of PDWs – or machine pistols or compact SMGs if you prefer. For only about double the size and weight of a pistol (but half the size and weight of an M4 Carbine) it offers perhaps ten times the effective range plus controllable automatic fire. The use of universally-available 9×19 ammunition is proving to be an important benefit, but if more range or penetration is required the gun can easily and reversibly be converted to the impressive and versatile 6.5×25 CBJ. For any military or law enforcement organisations contemplating a weapon in this class, this could be a winning combination.

More information about the 6.5×25 ammunition is presented on the CBJ Tech website at: www.cbjtech.com.

Brügger & Thomet’s website is: www.brugger-thomet.ch/.

Anthony G Williams is an independent ammunition consultant and co-editor of Jane’s Ammunition Handbook. He maintains a website at www.quarry.nildram.co.uk

The most successful military rifle and machine gun cartridges in service during the first four decades of the 20th century were powerful rounds of 7.5-8mm (.30-.32) caliber, with effective ranges of well over 1,000 yards. The U.S. .30-06, British .303, German 7.92×57 and Russian 7.62x54R are among the most famous and long-lasting, with the Russian round still being in service.

As early as World War I it had been realised by some observers that such long range performance was unnecessary for most infantry combat, and resulted in rifles which were excessively long and heavy and had too much recoil. However, the need to preserve the capability for long-range machine gun fire, plus military conservatism, combined to retain the status quo until late in World War II.

Experiments with less powerful cartridges were made in several nations in the 1920s and 1930s (notably in the USA with the .276 Pedersen), but it took the stimulus of war to prompt the adoption of the first of these to see service: the German 7.92×33 Kurz used in the MP 43/44/StG 44 selective-fire assault rifle. Captured examples inspired the Russians to develop the 7.62×39 M1943 round used in the Kalashnikov assault rifles and light machine guns. These rounds were not intended to replace the old high-powered cartridges, but to supplement them.

Instead of following suit, NATO countries started an apparently never-ending argument over the optimum characteristics of military rifle and machine gun ammunition. This article is intended to outline the history of this debate, which has been revived as a result of the conflict in Afghanistan.

The NATO Cartridge Trials of 1950

In the late 1940s it was decided to develop one standard rifle/MG cartridge for the new NATO alliance. There was immediately a serious disagreement over the caliber between Britain, Belgian and Canada on one side and the USA on the other. Britain and Belgium had been developing an intermediate round which, while still long-ranging, was smaller and less powerful than the old full-power cartridges. This was the .280 (7×43) which fired a 140-grain bullet at 2,415 fps. The .280 caliber (actually 7mm, with a .276 inch bore and .284 bullet) was a little larger than was thought ideal but was selected to meet American demands for long-range performance.

The USA had also been planning the replacement of the .30-06 cartridge and had developed the concept of a selective-fire “.30 Caliber Lightweight Rifle.” What they really wanted was the automatic .30 M2 Carbine but with the hitting power of the .30 Garand, at a weight of 7 pounds. It was intended to use a shorter cartridge than the .30-06, but was still required to have “a stopping and wounding power which shall not be less than that of the standard caliber .30 ammunition fired from the M1 at ranges of 400, 800, 1,200 and 2,000 yards.” The Americans accordingly ended up with what was simply a shortened version of the .30-06 with a very similar performance.

Comparative trials of the .280 and the new U.S. .30 cal (the T65) were held at Fort Benning in 1950. The .280 generally performed better, its lighter recoil making it more controllable in automatic fire, but the U.S. Army insisted on the adoption of its .30 cal. There was a major argument, the British even going so far as to formally adopt their own cartridge in August 1951 as the 7mm Mk 1Z, but it was never to enter service, being cancelled following American political pressure. Various efforts were made by the .280 supporters to increase the velocity of their ammunition, but in vain; NATO adopted a slightly modified T65 .30 cal cartridge as the 7.62×51.

The Hall and Hitchman Reports, Project SALVO and the SPIW

While the .30 caliber rifle and ammunition were still being developed, some American researchers were coming to different conclusions about the requirements for a military rifle. In 1950 the Ballistic Research Laboratory (BRL), an Army unit based at the Aberdeen Proving Grounds, was asked to investigate combat rifle effectiveness. The resulting report titled An Effectiveness Study of the Infantry Rifle was presented by its author, Donald Hall, in 1952. This was a theoretical study of the effectiveness of different calibres, which concluded that significant improvements in hit probability could be expected of a small-caliber, high velocity cartridge due to its flatter trajectory, and that there would also be benefits in a considerable reduction in ammunition weight.

In parallel with this study, the civilian Operational Research Office (ORO) of the U.S. Army’s General Staff examined what really happened in rifle combat. The resulting report on Project BALANCE by Norman Hitchman, the head of ORO’s Infantry Division, also emerged in 1952. Hitchman’s report was based on World War II combat records plus new data emerging from Korea. This showed that the average distance for aimed bullet hits was in the region of 75-100 yards with 80% of effective rifle and LMG fire being reported at ranges of less than 200 yards and 90% at less than 300 yards. Even worse for the Ordnance Department were tests of its .30 cal Lightweight Rifle prototypes which showed that the recoil was far too heavy, leading Hitchman to report that the cartridge was vastly overpowered and that automatic rifle fire was a waste of time and ammunition. This was five years before the selective-fire M14 in 7.62×51 caliber was officially adopted for US Army service.

Another controversial finding in the Hitchman report was that the accuracy of the rifle made no difference to the hit probability, because the typical aiming errors were so huge. This led in 1952 to the establishment of Project SALVO which, as well as studying conventional small-caliber cartridges, investigated a range of exotic ammunition options, including 12-bore shotgun cartridges loaded with 32 ‘ice pick’ projectiles (flechettes), multi-bullet loadings of .30 cal rifle cartridges with either two (Duplex) or three (Triplex) short bullets stacked on top of each other, and single-flechette rounds.

The promise of the flechette, which combined extremely high velocity with light recoil, led to the concept of the Special Purpose Individual Weapon or SPIW. This was the project which the U.S. Army hoped would provide a replacement for the M14, and huge resources were devoted to its protracted development during the 1960s. It would feature not only a burst-fire flechette rifle but also a 40mm repeating grenade launcher.

Four companies produced SPIW prototypes; AAI, Springfield, Winchester, and Harrington & Richardson. When tested in 1964, none proved satisfactory, falling well short of the specification in many respects. Only AAI and Springfield were asked to continue development. In 1966 the survivors were tested again, but the results overall remained very poor. While work continued until 1973, it was all in vain. The weight target proved impossible to meet, and the flechette rounds never achieved the accuracy nor the low cost required.

This was not the end of the flechette concept. This resurfaced in the Advanced Combat Rifle (ACR) tests in the late 1980s, in guns from AAI and Steyr, with other contenders from Colt (duplex bullet 5.56mm loading) and Heckler & Koch (4.7mm caseless G11). None managed the target of doubling the hit probability over the M16. Unconventional plastic-cased and caseless ammunition also feature in the U.S. Army’s current Lightweight Small Arms Technologies project. Time will tell whether this will be any more successful than previous attempts at advanced ammunition technologies.

The Small-Caliber Revolution

The costly failure of the SPIW project provided the opportunity for a much simpler approach. Even before the 1952 Hall report was published, experimenters at Aberdeen’s BRL and Development and Proof Services (D&PS) had been conducting a small caliber, high velocity (SCHV) research programme. Their work, which was used by Hall, focused on the improvements in hit probability which could result from a high-velocity rifle of .22 inch (5.56 mm) or smaller caliber.

From 1952 until 1956, a series of different small-caliber cartridges were developed in Project SALVO, with calibers ranging from .18 to .27 inches in Simplex (single bullet) and Duplex loadings. These experiments resulted in 1957 in a request from the U.S. Continental Army Command to ArmaLite (a division of the Fairchild Engine and Airplane Corporation) for a small caliber, high-velocity rifle. Eugene Stoner, the most famous post-WWII American military gun designer, went to work on the gun and cartridge, ultimately producing the AR-15 rifle designed to fire the new .223 Remington round. After various tests it was recommended in 1959 that the development of the AR-15 should be pursued as a replacement for the 7.62mm rifle – which had been formally adopted for service only two years before.

This did not immediately result in orders from the Army, which wanted the SPIW. The USAF placed the first order in 1960 to replace the .30 M2 Carbine used by their sentries. Adoption by the Army came about almost by accident, due to the cancellation of M14 production and the need to find a “stop gap” weapon to tide the Army over until the arrival of the SPIW. The AR-15 was officially designated M16 and adopted by the USAF in 1964. The US Army simultaneously chose it as a ‘limited standard’ formally adopting the M16A1 in February 1967. The 55-grain ball loading for the .223 Remington became the 5.56mm M193. As a result of the SPIW’s continuing problems, more and more M16 rifles were bought and this “stop gap” gradually became the Army’s new standard rifle. As the long-range performance of the little bullet was poor, the 7.62mm cartridge hung on in service, primarily in machine guns and sniper rifles, but the M14 was also retained by the USN.

For many years 5.56mm weapons were used by the USA (and purchased by various other countries) but not formally adopted by NATO. This changed following trials held between 1977 and 1980 to select a new NATO cartridge to supplement the 7.62×51. It was effectively impossible to propose any general-purpose round which might have replaced the 7.62×51, since only cartridges substantially smaller than the 7.62mm were considered.

These trials resulted in the selection of the 5.56mm as the next NATO cartridge with the designation 5.56×45 NATO. The Belgian SS109 loading (designated M855 in U.S. production) was chosen; this contains a hard steel element near the bullet tip and is heavier at 62-grains. The muzzle velocity is lower but the velocity loss is reduced, providing significantly improved long-range performance and penetration. However, complaints about a lack of terminal effectiveness of the “green tip” M855 have been going on since Somalia in the early 1990s. As a result, some limited use has been made of the MK262 heavy-bullet loading and work on developing more effective bullets continues – the latest example being the MK318.

The British have recently conducted tests of the effectiveness of 5.56mm ammunition and have determined that it is highly dependent on the impact velocity, which is directly linked to barrel length. The standard L85A2 rifle (20 inch barrel) has been found to have an effective range of 300 metres, while the L110 Para Minimi (about 14 inches – similar to the M4 Carbine) is only effective to 200 metres. Furthermore, experience in Afghanistan has revealed that 5.56mm bullets have negligible suppressive effect. Finally, U.S. experiments have revealed that 5.56mm bullets have poor barrier penetration and also sometimes fail to yaw on impact, inflicting only minor injuries. These findings provide ammunition to those who believe that the 5.56mm is fundamentally too small, and argue for a larger and more powerful cartridge.

The Search for the Optimum Caliber

An attempt to design an optimum military rifle round took place in the UK around 1970. The preferred solution was in 6.25mm caliber, firing a bullet of 100-grains at 2,680 fps. Tests revealed that this matched the 7.62×51 in penetration out to 600 meters and remained effective for a considerably longer distance, while producing recoil closer to the 5.56×45. However, the increasing use of the 5.56mm round meant that the 6.25mm stood no chance of being selected by NATO.

Immediately after the British 6.25mm experiments, the U.S. Army identified a need for an LMG cartridge which could reach out further than the 5.56mm M193. Various experiments resulted in the 6×45 SAW (Squad Automatic Weapon) which fired a relatively heavy 105-grain bullet at a velocity of 2,520 fps for optimum long-range performance. The SAW was abandoned in favour of the promised long-range loading for the 5.56×45 (which eventually arrived as the M855) and because fielding two similar calibers at squad level was felt to be inefficient.

Since 2000, two new attempts at a better rifle cartridge have been made. First on the scene was the 6.8×43 Remington SPC (Special Purpose Cartridge), which was a joint effort between Remington and a group within USSOCOM. After testing various calibers they settled on 6.8mm as having the best blend of characteristics. The 6.8×43 typically fires a 115-grain bullet at 2,590 fps. It not only demonstrates far superior terminal effectiveness and barrier penetration than the 5.56mm at short range; its advantage increases with range.

The other new cartridge is the 6.5×38 Grendel. Normally firing a 123-grain bullet at around 2,520 fps, this matches the 6.8mm in power but the heavier, more aerodynamic bullet matches the energy delivered by the 7.62mm M80 ball at long range, offering the potential to replace the 7.62×51 as well as the 5.56×45. Weight, power and recoil of these new cartridges are both roughly midway between the two existing service rounds.

Recent experience of asymmetric warfare in Afghanistan has re-emphasised the importance of effective small-arms fire, and at much longer ranges than expected. A British Army study has shown that more than half of all small-arms attacks by the Taliban (using weapons in 7.62x54R caliber such as the Russian PKM LMG) take place at between 300 and 900 metres. That is beyond the effective range of 5.56 mm weapons and has led to the allocation of 7.62mm machine guns and even sniper rifles to foot patrols, despite the unwelcome extra weight of guns and ammunition.

Over the next decade several NATO countries will be selecting new rifles, including the USA and the UK. This provides a rare opportunity to reconsider the ammunition they will be using. The ability of cartridges in the 6.5-7mm range to greatly improve on the 5.56mm, plus match the long-range performance of the 7.62mm with less weight and recoil, combine to make a strong case for one new, general-purpose rifle/MG round. Will the opportunity be seized this time? Watch this space!

(Anthony G Williams is an independent consultant, co-editor of Jane’s Ammunition Handbook, and co-author with Maxim Popenker of “Assault Rifle: the Development of the Modern Military Rifle and its Ammunition.” He maintains a website at www.quarry.nildram.co.uk)

There has long been a requirement for a personal defence weapon, or PDW, for soldiers whose primary duty does not involve carrying a rifle. They need something much smaller, lighter and handier which does not burden them or distract them from their main task. Originally, the main priority was for officers, who were almost invariably given revolvers or pistols; but handguns also found a place with cavalry and, later on, with soldiers such as gunners who might come under infantry attack or with tank crews whose space was at a minimum.

The Second World War saw extensive use of submachine guns chambered for pistol ammunition in both offensive and defensive roles, although they were not primarily intended as PDWs. While shorter than a rifle, they were often almost as heavy and troublesome to carry. A commendable effort to find a better solution was made by the US Army, resulting in the adoption of the light and handy .30 M1 Carbine chambered for a much smaller and less powerful cartridge than the M1 Garand rifle. This was so successful that it was often used in more offensive roles than originally intended, especially in its selective-fire M2 version, leading to some criticisms of the effectiveness of its ammunition. However, neither SMGs nor the Carbine replaced pistols, which remained in service alongside them.

A major change came with the adoption of small arms chambered for small-caliber high-velocity ammunition, the first and by far the most common cartridge being the 5.56×45. Its adoption by the USA in the 1960s, and by the rest of NATO in the 1980s, largely killed off the military use of both the .30 Carbine and most SMGs. Rifles and especially carbines in 5.56mm were lighter and handier than traditional SMGs while being a lot more effective. They even replaced pistols to a great extent in many armies, although the US Army has remained an exception.

While the standard NATO pistol/SMG cartridge has always been the 9×19, also known as the Parabellum or Luger, early experiments were also made with small-caliber compact cartridges. Among the many tried from the 1950s to the 1970s, three are particularly notable: the .22 APG, Colt .22 Scamp, and Colt .221 IMP.

The .22 APG (Aberdeen Proving Ground) was an M2 Carbine rechambered for a new 5.56×33 cartridge. This round was not a necked-down .30 Carbine but was based on a wider case, and it fired a 41-grain bullet at around 3,100 fps. This was only for comparative test purposes as a part of Project SALVO in the 1950s, but the other two were serious attempts at producing different kinds of personal defence weapons at the end of the 1960s.

The Colt .22 Scamp (Small Caliber Machine Pistol) was chambered for a 5.56×29 cartridge which fired a 40-grain bullet at 2,100 fps. The gun was basically a big pistol, gas-piston operated and with a plastic receiver to minimize weight, and was marketed, without success, as a .45 M1911 replacement. It could fire semi-auto or three-shot bursts at a cyclic rate of 1,500 rpm.

The Colt .221 IMP (Individual Multi-Purpose weapon) was initially chambered for an existing commercial cartridge, the .221 Remington Fireball designed for the big, bolt-action XP-100 pistol, and fired a 52-grain bullet at 2,500 fps. The ultimate version was intended to use a .17 cartridge firing a 25-grain bullet at 3,000 fps. It was developed at the request of the USAF who wanted a survival weapon, and was subsequently designated GUU-4/P. The gun had a most unusual layout; it was a bullpup without provision for a forward handgrip, the pistol grip being located close to the muzzle. The shooter was expected to steady the weapon by holding the receiver against his forearm with his non-firing hand, which led to the nickname “arm gun”. Like the Scamp, this made no progress although the layout was adopted for the 5.56mm Bushmaster Armpistol.

During the early 1990s, NATO became concerned that potential enemies were starting to issue body armor to their troops, which the 9mm ball rounds were unable to penetrate. As a result, a competition was arranged for a replacement for the 9mm which would have to penetrate a specified level of body armor (named the CRISAT target for the Collaborative Research Into Small Arms Technology project), defined as a 1.6mm titanium plate and 20 layers of Kevlar, while retaining sufficient energy to incapacitate the man wearing the armor, out to a range of 150 metres. Two different weapons were envisaged for this ammunition; a short-range (50 m) PDW weighing less than 1 kg (effectively a pistol) and a medium-range (150 m) close defence weapon weighing less than 3 kg (a compact SMG).

The penetration requirement forced the adoption of a small-caliber cartridge firing a high-velocity steel-cored bullet. The first contender was FN’s 5.7×28 round, as chambered in the P90 SMG and subsequently the Five-seveN pistol. The standard SS190 ball uses a 31-grain bullet fired at 2,350 fps (from the P90). The ammunition is lighter and smaller than the 9×19, allowing the pistol magazine to hold 20 rounds, and the P90 to carry 50. Recoil is also lighter than either the 9mm or the 5.56mm, making the weapons easier to shoot accurately.

The 5.7mm FN was subsequently challenged by Heckler & Koch who introduced their 4.6×30 cartridge at the end of the 1990s, initially available in the MP7 machine pistol (with the P46 pistol intended to follow). The current standard ball loading is the Ultimate Combat, which fires a 31-grain bullet at 2,360 fps (heavier than the original 26-grain Combat Steel). Various trials of the two cartridges were held between 2000 and 2003 and, while both met the requirements, the FN round generally came out ahead. However, the necessary consensus between NATO countries proved impossible to achieve so no standardisation has taken place: it is left to each country to make its own choice.

The Chinese apparently followed the same line of thinking as they introduced a new 5.8mm round for pistols and SMGs. This has the same calibre as their new rifle/MG cartridge, but the case is only 21mm long instead of 42mm, and is more slender. Performance is modest, but the relatively heavy bullet provides good penetration.

Other similar cartridges have emerged in recent years, so far without commercial success, such as the British .224 BOZ (10mm Auto necked-down, offered in a Glock 20 pistol), the Czech .17 Libra (based on a rimless version of the .22 Hornet case and chambered in a conventional SMG-type PDW), the Swiss Tuma MTE .224 VA (based on the 7.62×25 Tokarev case and offered in a machine pistol), the .225 JAWS (developed by Wildey for the Viper pistol on behalf of Jordanian Armaments and Weapon Supplies, with the same case diameter as the .45 ACP; .250, .300, .350 and .400 versions were also made) and, last but not least, the Swedish 6.5×25 CBJ, of which more later.

To date, the 5.7mm P90 and 4.6mm MP7 have achieved only modest military sales, mainly to specialised units rather than for use as general-issue PDWs. This means that the most common combination of self-defence weapons in Western service remains a short-barrelled carbine in 5.56mm (or equivalent) caliber with a self-loading pistol. However, there are problems with both of these weapons when used as PDWs which have been highlighted by the conflicts in Iraq and Afghanistan. These theatres lack front lines behind which soldiers can feel safe; attacks can come anywhere at any time. This means that all soldiers, including transport drivers and others who would not normally expect to be in a combat zone, need to be able to defend themselves.

The main problem with the pistol as a military PDW can be summed up in two words: hit probability. Even on the practice range, the maximum distance at which hits are likely to be scored is a small fraction of that of a carbine. In the stress of combat, accuracy deteriorates much more rapidly than with other weapons, and it is often stated that few soldiers are hit by aimed pistol shots at ranges of more than a few feet. While well-trained Special Forces can do a lot better than this, most PDW users will have little training or practice time with these weapons.

A carbine is much easier to shoot accurately, with the far more rigid three-point support of a shoulder stock and a forward handgrip as well as the pistol grip. Sights are also easier to use. The problem with carbines as PDWs is simply their size; they are not likely to be carried on the person unless danger is known to be imminent, and are more likely to be put somewhere out of the way while the soldier performs his primary task. As attacks can come without warning, this can lead to the guns not being immediately to hand when needed. There is also the risk of an “out of sight, out of mind” attitude, leading to the gun receiving little maintenance and performing (or not) accordingly.

Bullpup designs provide a much shorter overall length than traditional carbines, but even so they are no lighter and are generally too bulky to be carried conveniently when the soldier is engaged on other tasks. Even the FN P90 bullpup, while a clever design, is no lighter than a basic M4 Carbine (5.6 lbs empty) and is much bulkier to carry than a folding-stock machine pistol like the MP7.

One attempted solution to this problem is the KAC PDW. The gun is smaller and lighter than the M4 Carbine, and its 6×35 ammunition (based on the 5.56mm case) is claimed to match its effectiveness out to 300 metres with significantly less muzzle blast and recoil. However, it may still be considered too big to be routinely carried on the person, and it seems unlikely that an army would want to adopt another cartridge so close in performance to the 5.56mm, especially since the ammunition is also unsuited to use in a handgun. Similar objections would apply to the 5.56×30 Colt MARS carbine of the late 1990s and the current Indian MINSAS carbine project, which also fires a 5.56×30 round.

Having discussed the disadvantages of traditional weapons, what kind of characteristics would an ideal PDW have? There will be no agreed answer to this question, so what follows is just one personal viewpoint, based on many conflicting views studied over the years.

1. The PDW should be wearable, so that it is always immediately to hand when needed. This means it must be compact and light enough to be holstered (or similarly attached) without getting in the way or being a burden to the wearer. A weight of not more than 3.5 lbs (empty) seems a reasonable target.
2. It should have a shoulder stock and a forward handgrip to provide reasonable controllability and accuracy. The needs of compactness dictate that these should fold or telescope out of the way while the weapon is not in use; the gun must therefore be usable as a single-handed pistol in an emergency if there is no time to extend the stock and grip. In the past, some pistols have been offered with detachable stocks (which often doubled up as holsters) but these are really too cumbersome and slow to get into action, as well as not usually having a forward handgrip.
3. In the interests of compactness, the gun should use ammunition short enough for the magazine to fit into a pistol grip.
4. A very clear and easy-to use sight should be standard, preferably a red-dot zero-magnification holographic type.
5. The ammunition should be reasonably effective against both unprotected targets and those wearing (at least) soft body armor, but it isn’t realistic to expect a PDW round to match the performance of rifle ammunition. The effective range probably doesn’t need to be more than 100 yards or so.
6. Finally, it would be useful for selective fire to be available for its suppressive effect when caught in an ambush.

What is described here is clearly one of the modern breed of compact, lightweight SMGs or machine pistols. There are several types available, but the key issue is ammunition choice. Which is best suited to this role; traditional pistol ammunition or one of the new small-caliber high-velocity rounds like the 5.7mm and 4.6mm?

There is only one small-caliber gun in production which meets the above requirements: the HK MP7. There is a slightly wider choice of compact 9mm weapons, the most notable ones being the Swiss Brugger & Thomet MP9 (developed from the Steyr TMP – Tactical Machine Pistol), which is a little smaller and lighter than the MP7 at 3.1 lbs rather than 3.3, and the new STK CPW (Compact Personal Weapon) from Singapore. Russian firms have also introduced some machine pistols in this caliber recently, most notably the very compact PP-2000.

There is no doubt that the small-caliber rounds will penetrate more armor than traditional pistol ammunition, have a longer accurate range, are smaller and lighter so more rounds can be carried, and generate less recoil making them more controllable in automatic fire. These are all important plus points. However, against unprotected targets they seem likely to suffer from the same erratic effectiveness that afflicts the 5.56mm rifle round, only more so.

On the other hand, the effectiveness of the 9mm ball ammunition has also been questioned by US forces, with various attempts being made in recent years to open up competitions to replace the 9mm M9 with a .40 or .45 caliber pistol (the US Coast Guard has already adopted pistols in .40 S&W). Despite the criticisms of the 9mm, it may not be quite dead yet, and 9mm guns have scope for upgrading their armor penetration.

First, there are steel-cored armor piercing rounds for the 9mm which will get through soft body armor. If more penetration is needed the Russian approach is worth studying; they have recently adopted the 9×19 as their standard PDW round to replace the old 9×18 Makarov, with a composite AP bullet that holds together against soft targets but separates on hitting armor, the steel core penetrating alone. A high velocity is needed to achieve the penetration, which means that the bullets are light and will therefore lose velocity quickly, but they should be good enough for the required 100 yards. Two different loadings have been developed: the 7N21 (80-grain bullet at 1,510 fps) and the high-pressure 7N31 (65-grains at 1,970 fps). For those needing a longer effective range, a 9×21 round on similar principles is also in Russian service; the 7N29 loading fires a 104-grain bullet at 1,345 fps and is claimed to defeat armor consisting of two 1.2mm titanium plates and 30 layers of Kevlar at 50 meters.

Finally, it is possible, just by changing barrels, to switch from 9×19 to the experimental 6.5×25 CBJ, which in its standard loading fires a saboted tungsten alloy 4mm projectile weighing 31-grains at 2,720 fps from an eight-inch SMG barrel. This outclasses the penetration of the 5.7mm and 4.6mm PDW rounds (and even the 5.56mm M855) and has an effective range of 400 meters, but clearly its performance against unprotected targets is questionable although the spoon-tipped bullet variant should enhance tumbling.

The main drawback of the 9mm compared with the 4.6mm is its heavier recoil and the effect of that on controllability in automatic fire. Whether or not this is a significant issue would have to be tested in troop trials. Guns in .40 or .45 calibers (such as the .45 KRISS Super V) could of course receive the same enhanced penetration treatment, with composite armor-piercing bullets and saboted sub-caliber rounds. The downside is that the bigger cartridges reduce the magazine capacity and generate more recoil.

Any military weapon is a trade-off between conflicting requirements, and this is more true of PDWs than most. They need to be compact, light and handy, but also to have a high hit probability in semi-skilled hands and to be effective against unprotected men as well as having the potential for penetrating some levels of body armor. There is no correct answer to this conundrum, just a range of choices with different pros and cons.

Anthony G Williams is co-editor of Jane’s Ammunition Handbook, co-author (with Maxim Popenker) of “Assault Rifle” and “Machine Gun” and maintains a website at www.quarry.nildram.co.uk

By Anthony G. Williams

Today there are only six cartridges used in rifle-calibre machine guns in the world’s major armies: the 7.62x54R Russian, 7.62×51 NATO, 7.62×39 Russian, 5.45×39 Russian, 5.56×45 NATO and 5.8×42 Chinese. Of these, only the first two are traditional “full power” rounds, a type which until World War II was used in almost all rifles and machine guns. Yet during the 20th century many different full-power rifle-calibre cartridges were developed and used in machine guns, and this article describes the ones which saw significant military service.

The definition of “machine gun” can be stretched to include the Gatling and other manually operated repeaters that were developed during and after the period of the American Civil War. However, this article will be focusing on the small-calibre high-velocity rounds that entered service in recoil or gas-operated machine guns from the last decade or so of the 19th century. The first of these guns was the famous Maxim which was first adopted by Italy and Austria in 1887, used by many nations, and redesigned and improved in the UK (Vickers), Germany (MG 14 Parabellum), Russia and Switzerland. The Maxim was offered in a wide range of calibres to suit the national preferences of its purchasers, as were other widely popular machine guns such as the Madsen (from 1902), Schwarzlose (1905) and the interwar FN-built Brownings. Other much-exported guns, particularly the Hotchkiss models (the first of which was adopted in 1897), were more often sold in their original calibres.

It is worth noting that a few of the older manually-operated guns were adapted to use the modern smaller-calibre ammunition. Conversely, some of the older black-powder rounds were updated with smokeless powder, chambered in modern MGs and remained in use until after World War I. These included the French 11x59R Gras rifle cartridge, which was loaded with incendiary bullets and chambered in Hotchkiss and Vickers MGs for shooting at hydrogen-filled observation balloons and airships during the Great War. The British Royal Navy also retained Maxim machine guns in a cordite-loaded version of the .45 inch Gardner-Gatling calibre until after that war.

These were rare exceptions. By the beginning of the Great War, most major armies had switched to using the new small-calibre rifle rounds in automatic machine guns. These mainly fell into two groups: 7-8mm and 6-6.5mm calibre. Those developed in the 19th century and the very beginning of the 20th were initially loaded with heavy round-nosed bullets, after which lighter spitzer (pointed) bullets, fired at higher muzzle velocities, were introduced. Most of the earlier cartridges were then modified to use spitzer bullets (in some cases the opportunity was taken to alter the cartridge dimensions as well), but a few retained only round-nosed bullets until the end of their service lives, the best-known of these being the Italian 6.5mm Carcano.

Of the 6-6.5mm group, the US Navy’s 6mm Lee had the smallest calibre to see service until the 1960s, although the cartridge case was relatively large. It dates back to 1895 and was really ahead of its time, as propellants available then could not extract the potential of the cartridge, which developed a muzzle energy of less than 1,650 ft/lbs. The only MG chambered for it was Browning’s first service design, the Colt Mk 1 (also known as the M1895 and, more popularly, the “potato digger”), and the cartridge was replaced twelve years later by the US Army’s .30-06 round. The other rounds in this group were all of 6.5mm calibre and broadly comparable in size and power; the Japanese 6.5x50SR Arisaka (round-nosed Type 30 adopted in 1897, Type 38 spitzer loading in 1905), Italian 6.5×52 Carcano (1891), Dutch/Romanian 6.5x54R Mannlicher (1892), Greek 6.5×54 Mannlicher-Schönauer (1903) and Swedish 6.5×55 Mauser (1894 – also used by Norway, Denmark and Luxembourg). All of these developed around 1,800-2,100 ft/lbs muzzle energy. Of these, the 6.5×55 was the biggest, most powerful and most long-lived, and remains a popular round for commercial hunting rifles.

The larger calibre group showed a little more variety in performance, typically developing muzzle energies in the 2,200-3,000 ft/lbs range in the later spitzer loadings. The dominant rounds throughout this period were the German 7.92×57 first developed in 1888 as the Patrone 88/8, although modified to take a spitzer bullet (S-Patrone) of slightly larger diameter in 1905, the British .303 inch (7.7x56R) of 1889 (the round-nosed bullet replaced by the Mk VII spitzer ball in 1910), the Russian 7.62x54R of 1891 (spitzer loading in 1908), and the American .30-06 (7.62×63) of 1906. The spitzer-bullet .30-06 replaced the slightly longer .30-03 (7.62×65 with a round-nosed bullet) of 1903 which had in turn replaced the .30-40 Krag (7.62x59R) of 1892. Of these, the 7.92mm Mauser and the .303 were used by many nations prior to and during World War 2, the .303 even by Italy and Japan as a consequence of interwar exports of Vickers and Lewis aircraft MGs. The 7.62x54R of course remains in front-line military service in Russia, China and many other countries to this day, while the 7.92×57 and.30-06 cartridges are very popular in hunting rifles. These were supplemented by many other cartridges, however: it appeared to be fashionable for each nation which could afford it to have its own unique rifle/MG round. In addition, some “rifle calibre” rounds were specifically developed for machine guns.

The French 8x50R Lebel was actually the first modern smokeless-powder round to be adopted, with the flat-nosed Balle M bullet in 1886, and in 1898 also introduced the first military spitzer loading, the famous solid brass Balle D, which was also the first to have a boat tail. It was replaced in service by the short-lived 7.5×58 in 1924 before that was in turn replaced by the slightly modified 7.5×54 Model 1929 five years later, to reduce any confusion between the 7.5×58 and the 7.92×57. The new cartridge was, however, very similar to the Swiss 7.5×55 adopted in 1911 with a boat-tailed spitzer bullet to replace the earlier round-nosed 7.5×53 of 1889. The 7.5×54 remained in French service until replaced by the 7.62×51 in the 1970s, while the 7.5×55 is still in Swiss service and is available in military and hunting loadings.

The German-developed 7×57 Mauser, a slightly necked-down version of the older 7.92×57, saw service with Spain from 1892, several South American nations and Serbia, in various different machine guns. The 7mm remains a deservedly popular commercial hunting cartridge, being regarded as one of the most useful rounds for anything short of heavy and dangerous game. Another popular military cartridge was the 7.65×53 Mauser of 1889, also known by the names of the principal user countries as the Belgian, Argentine and Turkish Mausers: in addition it was used by some other South American countries. A spitzer bullet loading was not adopted until the 1920s. Despite this widespread military use it has never achieved much popularity as a commercial hunting round.

Other rifle rounds to see service in machine guns include the 8x50R Mannlicher first adopted by the Austro-Hungarian Empire in 1886 (and subsequently used by Bulgaria), the 8x52R Siamese Mauser of 1923, and the 8x58R Krag-Jorgensen of 1889 (spitzer bullet loading 1908) used by Denmark, Sweden and Norway.

Several nations decided to upgrade the performance of their machine guns by adopting new rounds specifically for them. Most such changes were made in the interwar period, although the Dutch had used their unique 7.92x57R as a special-purpose machine gun round since 1908. The Japanese first adopted the 7.7x58SR in its Type 89 version (in 1929), later replaced by a modified loading, the Type 92: later still came the rimless 7.7×58 Type 99, used in rifles as well as MGs. Norway adopted the 7.92×61 in 1929, Austria, Hungary and Bulgaria the 8x56R Solothurn from 1930 (unusual at that late date for using a rimmed case), Sweden the 8×63 in 1932, and Italy the 8×59 Breda in 1935. In some cases rifles chambered for these rounds were also made, but with the main exception of the 7.7mm Type 99 these were primarily to provide MG troops with commonality of ammunition. In addition, in 1938 the Italians adopted the Breda M38 in their new 7.35×51 rifle cartridge (the 6.5×52 Carcano necked-up to accept a larger, spitzer, bullet), but before the change to the new calibre had made much progress, the Second World War broke out and caused the changeover to be stopped.

The end of the Second World War saw most of these old calibres gradually phased out, although some lingered for a few decades. New “intermediate” cartridges primarily intended for selective-fire assault rifles were developed, and these were soon used in light machine guns. The two remaining full-power rounds, the old 7.62x54R Russian and the 1950s 7.62×51 NATO, are still extensively used in GPMGs and specialist rifles and look as if they will continue in those roles for a long time to come. Nearly all of the rest have either vanished into history or, in a few cases, are surviving by virtue of their popularity in hunting rifles.

(This article is based on excerpts from the book “Machine Gun: the Development of the Machine Gun from the 19th Century to the Present Day”, by Maxim Popenker and Anthony G Williams, published by The Crowood Press (UK) in July 2008. Anthony G Williams is Co-editor of Jane’s Ammunition Handbook and his website is at www.quarry.nildram.co.uk.)

The US Army’s programmes for developing two different 25mm grenade launchers – the shoulder-fired XM25 from Alliant Techsystems and the crew-served XM307 ACSW (Advanced Crew-Served Weapon) by General Dynamics – are probably the most ambitious small arms projects in existence. They are meant to revolutionise the effectiveness of small-arms fire by detonating HE/fragmentation grenades directly over the target, thereby greatly increasing the number of casualties, not just of standing men but also those hiding behind cover. Such rounds are known as HEAB (High Explosive Air Burst) or ABM (Air Bursting Munition).

To achieve this requires some sophisticated technology. The XM307 is fitted with a day/night sight with a laser rangefinder, a ballistic computer and a fuze-setter. The gunner first lases the target to establish the range (this can be overridden if the target is at a slightly different distance than the aiming point); the system then takes atmospheric conditions and weapon tilt angle into account before indicating the aiming mark in the sights. The gunner can set the fuze mode for airburst, PDSQ (point detonating super-quick), PD delayed-action or deactivate; it also contains a self-destruct element. The projectile fuze measures the distance by counting the number of rotations: its spin rate is 21,000-28,000 rpm. The XM25 uses the same technology, with a shorter, lower-velocity cartridge limiting the range to around 700m rather than 2,000m.

The XM307 was originally intended to replace most of the .50 M2HB and 40mm Mk 19 AGLs, while the nearest comparators to the XM25 are the much bulkier six-shot revolvers chambered for the low-velocity 40mm grenade round, such as the Milkor MGL, adopted by the USMC as the M32. Adoption of the XM25 might therefore be expected to lead to a reduction in the use of the 40mm LV (low velocity) weapons, if not their eventual disappearance.

The manufacturers of 40mm GLs and ammunition are not taking this lying down, however, and have come up with a range of new developments to keep their products attractive.

Ammunition for Shoulder-Fired Grenade Launchers

The 40x46SR low velocity (LV) grenade round has now been around for almost half a century, originally chambered in stand-alone single-shot guns like the M79, but subsequently in underbarrel grenade launchers (UGL) such as the M203, and more recently the six-barrel revolvers mentioned above. The muzzle velocity is only 250 fps, limiting the maximum range to about 400m.

The original round fired was the M406 HE/fragmentation type, and High Explosive Dual Purpose (HEDP) rounds have also been available for some time, enabling these launchers to be used to tackle light armour. Some recent developments have considerably extended the versatility of this round. From Arcus of Bulgaria comes the AR476 “Anti-Diver” grenade which has a time fuze which is set on impact with the water, detonating the HE at a stated depth of between 5 and 12 metres and with a claimed lethal radius of 12m. They have also introduced the AR466 “Bouncing” ABHE grenade which on impact is kicked back up into the air by a small nose charge before detonating, to increase the lethal radius – not a new idea, but a very much cheaper way of providing some of the effectiveness of the sophisticated HEAB systems. A similar RLV-FJ “Jump” round is offered by Arsenal, also of Bulgaria – a country which appears to be innovating with enthusiasm in this field.

More effective conventional ammunition has also been developed, with the latest trend being Medium Velocity (MV) rounds, with the muzzle velocity increased to between 350 and 410 fps, thereby doubling the effective range. Recoil is claimed to be similar to that of a 12 gauge shotgun, and well below that of a rifle grenade, and they are designed to be used in many existing LV systems. At a range of 150m the mid-range trajectory will be halved to about 3m and flight time is reduced. The first in the field was Martin Electronics’ “Mercury”, which is significantly longer than standard 40mm HE rounds to make room for a larger HE charge, doubling the destructive power as well as the range of the conventional M433 HE grenade. Nammo Raufoss, Heckler & Koch and now Denel of South Africa are also developing MV ammunition, while Arcus have developed “extended range” versions of their HE and ABHE products, capable of about 600m.

IMI and STK are even developing High Explosive Air Burst LV rounds to deliver the same effects as the XM25, although these do of course need to be used in conjunction with special sights with a laser rangefinder and fire control computer, and also a launcher modified to include an electronic fuze setter. IMI have developed the compact and lightweight Orion sight which offers these facilities and can be fitted to any rifle in conjunction with a modified UGL.

Martin Electronics have also introduced a thermobaric round, the DRACO; a type of explosive which is proving particularly popular in some larger weapons in use in the Middle East because of the effectiveness of its high blast overpressure in enclosed spaces such as buildings and caves. The round is very expensive, however, so attention is now being focused on the much cheaper Hellhound.

The peacekeeping roles which armies frequently have to adopt have generated growing interest in Less-Lethal ammunition for riot control and similar policing activities. Many manufacturers now offer a very varied range of irritant chemical, impact, combined and paint marker ammunition too extensive to describe here. Although such munitions have traditionally been used in specialised 37/38mm riot guns, they are increasingly available for the 40mm LV grenade launchers – and, in a few instances, for the 40mm HV AGL as well.

Other types of rounds which are not directly lethal include various smoke and flare types. There are also some novel developments, most notably the observation rounds containing parachute-borne video cameras that send pictures directly back to the operator, providing an instant view of what lies over the hill or around the corner. Both STK (with the SPARCS) and Martin Electronics (with the HUNTIR) have developed such rounds for 40mm LV grenade launchers, while the Rafael Firefly, still in development, is equipped with folding “wings” rather than a parachute.

Many of the new rounds are longer than standard, at up to 5.5 inches. In contrast, ammunition for the semiautomatic XM25 is limited in size (the maximum length is only about 3.5 inches), and cannot hope to emulate the variety of types now available for the 40mm LV GLs, which will be with us for the foreseeable future.

40mm AGLs

The success of the original 40mm LV grenade rounds rapidly led to the development of fast-firing weapons chambered for them, but almost as quickly the need for greater range was realised, so the 40x53SR high velocity (HV) cartridge was developed. This had the muzzle velocity increased to around 800 fps which, in conjunction with a heavier grenade (about 240g compared with 180g), increased the effective range out to 2,000m. The first automatic grenade launchers (AGLs – also known as grenade machine guns or GMGs) chambered for this round were externally powered and designed for installation in helicopters: the M75 and M129 both seeing service in Vietnam. Far more important, however, was a self-powered design, the Mk 19. This was developed in the late 1960s as a USN project but was subsequently adopted by other services, as well as achieving substantial export sales.

Since then, and particularly since the 1990s, a number of rival AGLs have emerged from several different countries: the Spanish Santa Barbara (now General Dynamics Santa Barbara Sistemas) LAG 40 SB, the Singapore Technologies Kinetics (STK) 40AGL and Light Weight AGL, the Heckler & Koch HK40 GMG (recently bought by the British Army), South Africa’s Denel Y3 AGL, and other weapons from Romania, Poland, Turkey and Pakistan. Of most significance to the USA is the CG40, a joint project between three companies, commencing in 1995: Nammo (ammunition), General Dynamics Canada (Fire Control) and Saco Defense (now a part of GD) who developed the gun and dealt with system integration. Some 400 are in service with US special forces, ordered between 2001-5, under the designation Mk 47 Striker.

The HV ammunition used in these guns has not shown the variety found in the LV rounds, partly because of the narrower range of uses of the AGLs and partly because the need to function in an automatic mechanism restricts the characteristics – and particularly the overall length – of the cartridge. However, a great deal of attention is now being paid to the development of the same kind of airburst technology as that being tested in the XM307.

The way is being led by Nammo Raufoss, who have developed HEAB ammunition as a part of the CG40 project, under the designation PPHE (Programmable Pre-fragmented HE). The gun was designed for this from the start, the necessary systems being integrated into the weapon. These include an image-intensifying video sight linked to a laser rangefinder and incorporating a ballistic computer to indicate the exact aiming point, and an electronic fuze setter by the gun breech. When used with the appropriate ammunition fitted with the Mk 438 programmable time fuze, the system sets the appropriate time delay on the fuze while it is in the chamber (the gun fires from a closed bolt) so that the grenade bursts directly over the target. The gun can also use conventional point-detonating 40x53SR ammunition, with which the advanced sights are still useful in providing a high level of accuracy. The Mk 285 HEAB projectile produces fragments which are mainly distributed sideways and backwards to catch troops behind cover, rather than forwards as with a conventional grenade. An initial order for 39,000 of this round has been placed for use in the Mk 47 Striker, with deliveries expected to be completed by early 2008.

Nammo are also working on a variation of this system for guns, such as the HK40 GMG, which fire from an open bolt. The chosen system is radio frequency programming, the fuze being set about 4 to 5 metres after the grenade has left the muzzle. Since all of the system requirements are contained within a single sight/fire-control/programming unit, this can be fitted to any gun able to mount the unit.

There is yet a third HEAB system, from STK of Singapore; the ABMS (Air Bursting Munition System), which can also be fitted to existing 40mm AGLs. This was developed in conjunction with Oerlikon-Contraves Pyrotec AG of Switzerland, who adapted the technology developed for their 35mm AHEAD cannon ammunition. As with AHEAD, the fuze-setting system is attached to the muzzle and sets the fuze as the grenade leaves the barrel. Like the Nammo systems, special grenades are used with an all-round fragmentation pattern, so they throw fragments behind them as well as in front and to the sides; the Oerlikon/STK type contains 330+ tungsten balls, each weighing 0.25g and intended to penetrate at least some grades of body armour. The effective range of the system is 40 to 1,600m.

In the rush to airburst systems, the value of the conventional (and much cheaper) ammunition has not been forgotten. Nammo have developed a ‘product improved’ M430 HEDP round at the request of the USMC, who have asked for a mechanical self-destruct fuze, a modified (NICO type) propulsion system, insensitive munition (IM) properties using a PBXN-11 main charge, additional incendiary after-armour effect, penetration improved from three to four inches of RHA, and a reduced safety zone to prevent the base of projectile from being blown back towards the gunner (the current limitations being 310m in peacetime, 75m in wartime). Internal Nammo qualification of this round is expected in spring 2008.

While the 25mm XM307 offers certain advantages, notably gun and ammunition weight plus a much flatter trajectory and shorter flight time, the 40mm AGLs clearly have a lot of life in them yet. Their ability to fire inexpensive standard ammunition as well as sophisticated HEAB rounds means that they are likely to remain popular long after the XM307 enters service.

(Anthony G Williams is Co-editor of Jane’s Ammunition Handbook, and maintains a website at http://www.quarry.nildram.co.uk)

Throughout the first half of the last century, the great majority of sniper rifles were more or less modified versions of the standard military rifles, chambered for the standard rifle/MG cartridge. The growth of self-loading rifles during and after World War 2 saw sniper rifles departing from this tradition as the bolt-action type was generally retained for its greater accuracy. A further difference came when the standard rifles adopted lower-powered intermediate cartridges, much less suited to the business of long-range sniping. During the second half of the century, the military sniper rifle became a purpose-designed specialist instrument, capable of the highest practicable accuracy. This was usually complemented by precision-made ammunition, often loaded with heavier low-drag bullets, such as the 7.62×51 M118LR.

These developments have resulted in some superb equipment, but trends in accurate aimed fire can now be detected in two different directions: one is for the shorter ranges to be addressed by accurised self-loading guns providing faster repeat shots; the other is for guns firing more powerful cartridges being selected to increase the effective range. This article is concerned with the cartridges developed for meeting the second of these needs: long-range sniping.

To achieve a significantly longer range than the usual 7.62×51 requires at least a larger cartridge case to generate a much higher muzzle energy, and preferably a larger caliber as well; other things being equal, heavy large-caliber bullets retain their velocity better and are less affected by cross-winds. This was recognised by the first attempts to fire accurately at very long range; which often used anti-tank rifles of 13-14.5mm caliber. In fact, as early as the Great War, the 13mm Mauser M1918 anti-tank rifle was used in the counter-sniping role, although in this case the motivation was not so much to achieve long range as to punch through the armour plates being used to protect Allied snipers. The Korean War saw Soviet 14.5mm PTRD rifles being used for long-range fire, as well as and, on the US side, some experiments with .50 BMG guns. However, the guns were usually not that accurate and, even if they were, the standard production MG ammunition certainly wasn’t.

A change came in the 1980s from two different sources in the USA. One was the adoption of long-range anti-materiel rifles in .50 BMG caliber, not primarily for sniping but for attacking vehicles and other inanimate objects, normally using standard API or (later) Multipurpose MG ammunition. The other was the establishment of the .50 Caliber Shooters Association, promoting the use of this caliber for long-range civilian shooting, which inspired much more accurate rifles and ammunition. In combination, these two developments led to the use of .50 BMG rifles for long-range sniping as well as anti-materiel use.

There is a problem, however: the .50 BMG rifles and their ammunition are necessarily very big and heavy, not ideal for the sniping role. Many believed that a smaller, but still powerful, caliber would do that job more efficiently. As a result, specialised long-range sniping rifles are now available in several competing calibers. The ones described in this article are those offered in military sniper rifles; though there are a host of wildcats in addition. Furthermore, some anti-materiel rifles are also offered in the Russian calibers of 12.7×108 and 14.5×114, but these will not be considered here.

A high muzzle velocity is an advantage in long-range sniping, but that alone is not enough. As ranges extend, it is the ability of the bullet to retain its velocity which becomes increasingly important; bullets that slow down gradually are far more useful than those which rapidly shed velocity. To achieve this, the bullet needs a high ballistic coefficient (BC). This is achieved partly by using a bullet of exceptionally streamlined shape, and partly by making it heavy. It is worthwhile sacrificing some muzzle velocity in order to use a bullet with a higher BC.

The key yardstick for long-range sniper ammunition is the range at which the bullet drops below the speed of sound. This is important for two reasons. The first is because that provides a quick proxy for the trajectory and time of flight of the bullet; and the flatter the trajectory and the shorter the flight time, the greater the hit probability, other things being equal. The second is that dropping back through the transonic zone usually disturbs the flight of the bullet, adversely affecting accuracy, although this effect is minimised with the very low drag bullets developed for the more specialised calibers. To give an example, the 7.62×51 147-grain M80 standard NATO ball bullet is fired at a muzzle velocity 200 fps higher than the 175-grain M118LR, but drops to subsonic velocity at around 875 meters compared with 950 meters for the heavier and initially slower bullet.

The table gives basic measurements and typical performances for the cartridges being discussed. The muzzle velocities and energies will of course be affected by the barrel length selected: figures quoted here are at the high end of the range. It is also worth remembering that some of the more specialised cartridges may develop higher chamber pressures than would be acceptable for a standard MG round, pushing their performance up quite significantly.

.300 Winchester Magnum

This was first developed as a commercial hunting round in the early 1960s. Work on adapting this cartridge for the long-range sniping role was undertaken by the USN in the 1980s to meet a special operations requirement for a rifle which would extend the 800 meter effective range of the 7.62×51 out to 1,200 meters. The standard loading uses a Sierra Match King bullet, which retains minute of angle accuracy out to at least 1,000 meters. This is in US service for special purposes.

.338 Lapua Magnum

Originally developed in the mid 1980s by the Research Armament Company as a long-range sniper round to meet the same USN requirement as led to the use of the .300 Win Mag described above, this was subsequently adopted by Lapua and is now made for both military and civilian requirements. The normal maximum range is regarded as 1,200 meters, but in ideal conditions it can reach out to 1,600 meters, the distance at which the bullet becomes subsonic. Many feel that this is a very practical round for sniping since the rifles are not much bigger or heavier than the .30 caliber weapons, and its use is spreading. The British Army adopted some Accuracy International rifles in this caliber some years ago, and recently announced its intention of replacing many of its 7.62mm sniper rifles by acquiring more of the .338 guns.

.375 CheyTac

The most recent addition to this field, this is simply the .408 CheyTac (see below) necked-down to the smaller caliber. It has been calculated that for the most potent loading, shooting 375-grain Lost River Ballistic Technologies solid copper-nickel alloy bullets at 3,050 fps muzzle velocity, the supersonic range would be around 2,230 meters. Wildcat versions of this cartridge, using very long 408-grain Viking bullets developed by Lutz Möller and fired at 2,854 fps, are claimed to achieve astonishing performances, with the supersonic range in excess of 3,000 meters.

.408 CheyTac

This round was developed by Cheyenne Tactical, LLC and introduced in 2001 in conjunction with its own range of sniping rifles. The original basis for the cartridge was the old .505 Gibbs big-game hunting round, but it has been much modified as well as necked down. The standard 419-grain Lost River Ballistic Technologies bullet remains supersonic and effective to 1,900-2,000 meters. A different loading, firing a lighter (305-grain) bullet at a velocity of 3,250-3,500 fps, has been developed to provide a flatter trajectory and shorter flight time out to 1,000 meters. The CheyTac rifle has reportedly been tested by the USMC, and sold abroad for Special Forces use.

.416 Barrett

This was developed recently by the famous maker of .50 caliber rifles, reportedly in irritation at a California decision to ban .50 cal. weapons. The basis of this round is the .50 BMG case, which is shortened and necked down. The performance is highly impressive, the standard bullet remaining supersonic to more than 2,250 meters. This bullet takes 2.5-2.6 seconds to reach 2,000 yards (1,830 meters) compared with 3.0 seconds for the .408 CheyTac. No service use is known at present.

.460 Steyr

This round pre-dates the .416 Barrett, being developed in the early 2000s by the Austrian Horst Grillmeyer, but adopts the same principle of shortening and necking down the .50 BMG case, this time to .458 caliber. Little information about the performance of this round has so far emerged, but very specialised long-range bullets have been developed for it, so it is reasonable to assume a supersonic range in the region of 2,000-2,500 meters. As with Barrett and their .416, Steyr Mannlicher can easily make weapons in this caliber by fitting new barrels to the .50 BMG rifles which they already offer. This also means, of course, that the guns are as big and heavy as .50 BMG rifles, so the customer will need to decide whether the ballistic advantages of these cartridges are sufficient to outweigh the loss of the wide range of ammunition types available in .50 caliber.

.50 BMG

The history of this old warhorse is too well known to repeat here. Apart from its usual MG loadings, specially accurate bullets and loadings have been developed for use in rifles, for example the Sniper Elite listed in the table above. Most military sniper loadings are limited in their performance by being restricted to matching the trajectory of standard .50 MG rounds, which means that they only remain supersonic out to 1,500-1,600 meters. More specialised loadings reveal a lot more potential. For example, the Hornady A-MAX 750-grain bullet, shown in the photograph, remains supersonic out to 2,250-2,300 meters despite having a muzzle velocity of only 2,700 fps.

In conclusion, the long range sniper is spoiled for choice to a degree never seen before, and the drive to achieve the best possible performance and accuracy out to astonishing distances is pushing forward the boundaries of bullet design and ballistics.

Anthony G Williams is an author and military technology consultant, specialising in small and medium calibre ammunition. He maintains a website at http://www.quarry.nildram.co.uk

By Anthony G. Williams

The Great War of 1914-1918 saw the first substantial use of aircraft in a major conflict. At the beginning the aircraft were almost all frail, underpowered devices that could barely lift themselves and their one or two crew into the air, and carried no armament except for the crew’s personal weapons. By the end of the conflict, heavy bombers carrying multiple defensive machine guns contested the air with fast and agile fighters, typically armed with two fixed machine guns synchronised to fire through the propeller blades. As well as ball rounds these guns fired a variety of specially developed ammunition, loaded with armour-piercing, incendiary and even explosive bullets.

Although machine guns specially designed for the needs of air fighting were being developed at the end of the war, none of these had time to get into service. So with the exception of a few large-calibre cannon, the air war was fought with more or less modified versions of the guns used on the ground by the army.

The Austro-Hungarian Empire, with its capital in Vienna, was one of the major combatants in the Great War, fighting alongside Germany and the Ottoman Empire against France, the United Kingdom, Russia (until 1917), Italy (from 1915, initially only against the Austro-Hungarian Empire), and the USA (from 1917). Defeat in the war led to the break-up of both the Austro-Hungarian and Ottoman Empires.

The standard machine gun of the Austro-Hungarian armed forces was the Schwarzlose. This was designed by a German, Andreas Wilhelm Schwarzlose, who took out the first patent in 1902. It was adopted by the Empire in 1905 as the M05 (Model 1905) and manufactured at the Osterreichische Waffenfabrik Gessellschaft in Steyr, Austria. An improved model, the M07, replaced the M05 two years later, to be replaced in production by the further-modified M07/12 five years after that. However, the older versions remained in service.

The Schwarzlose was unusual by comparison with the common locked breech short-recoil (e.g. Maxim) and gas-operated (e.g. Hotchkiss and Lewis) guns in that its mechanism used a form of blowback, in which the gas pressure in the barrel forces the cartridge case backwards, pushing the unlocked bolt to the rear of the gun. In its simplest form, the blowback mechanism is restricted to very low-powered cartridges because it is necessary for the inertia of the bolt to hold the case in the chamber until the projectile has left the barrel, otherwise high-velocity burning gas will burst from the breech to the discomfiture of the firer. With high-pressure military rifle cartridges, the weight of bolt required would be so heavy that the rate of fire would be very low.

Various solutions to this difficulty have been tried, because blowback weapons are attractively simple and cheap to manufacture. One is the retarded blowback, in which an additional mechanism resists the initial rearward movement of the bolt, and this was the approach adopted by Schwarzlose. His design utilises an elbow joint attached to the bolt by one arm with the other arm pivoted to a fixed axis on the receiver. The effect of this mechanism is to force the initial rearward movement to operate under severe mechanical disadvantage, delaying the opening of the breech until the bullet has left the barrel. Even so, the cartridges it used were so powerful that the breech still opened too quickly. The solution was to shorten the barrel to 20 inches (compared with 28 inches for the Maxim) so that the bullet left the muzzle sooner before the breech could open. It was belt-fed, using a fabric belt. The simplicity of the mechanism kept the cost down to about half that of a Maxim, and the gun was subsequently adopted by several other European countries in a variety of different calibres. The ruggedness and reliability of the Schwarzlose made it a popular gun and it had a long life, though the main problem being the sensitivity of the mechanism to ammunition quality. The Dutch were still making it in 1940, and it was being used at least until 1945 as a second-line weapon in Italy and Hungary.

In army and naval use, the gun is recognisable by the short and wide water-filled barrel jacket, the large conical flash-hider attached to the muzzle (the short barrel presumably resulting in a much bigger muzzle flash than usual) and the curved shape of the back of the receiver. As with all blowback guns there is no primary extraction, so the gun was fitted with an oil tank and the chamber was sprayed with oil before each round was chambered in order to facilitate case extraction. This mechanism was the source of some discomfort in aircraft use when Schwarzloses were mounted in front of the pilot, as he received a constant spray of oil in his face whenever the guns were fired. In at least one installation – in the Albatross fighter – a metal shield and drainage tube were fitted to catch and dispose the oil.

The cartridge in use in the Austro-Hungarian Empire was the 8x50R Mannlicher, developed in 1886 by the Georg Roth ammunition factory of Vienna together with the Vienna Armory, and one of the first of the small-calibre military rounds designed to use the new smokeless powder. The US equivalent was the .30-40 Krag of 1892. The initial loading featured a heavy (244-grain) round-nosed bullet fired at 2,030 fps, although some later specialised loadings, such as the M.08 armour-piercing and the M.17 and M.18 incendiary types, used pointed bullets. There was also an explosive bullet with a blunt nose and a waisted body. These explosive and incendiary types were intended for use against hydrogen-filled observation balloons, initially from ground-fired guns and later from aircraft.

The Schwarzlose as an Aircraft Gun

The Schwarzlose was not an obvious choice for an aircraft gun, being bulky, heavy (at around 43 pounds) and initially slow-firing at around 400 rpm (500 rpm for the M07/12). However, except for a few imported Madsens, Bergmanns and LMG 08/15s, it was all the Austro-Hungarians had available so it was adapted for the task. At the start of the conflict the Empire also pressed into aerial service some Schwarzlose M12s intended for export to Greece, chambered for their 6.5×54 Mannlicher-Schönauer cartridge. This fired a 160-grain round-nosed bullet at 2,230 fps. The M12 guns were lighter, being air-cooled, and were used as flexibly-mounted defensive weapons, but the small bullet was less effective so these were eventually replaced by 8mm guns.

The first change to the gun for aircraft use was the removal of the flash hider. The next concerned the water jacket. Cooling water was not necessary for an aircraft gun: the combination of short bursts of fire and a strong wind keeping the barrel cool enough. So the jacket was frequently emptied of water and fitted with large slots to allow air to circulate. Unlike the Vickers/Maxim short-recoil guns in which the front of the barrel jacket was needed to support the moving barrel, the only other function of the jacket in the fixed-barrel Schwarzlose was to hold the foresight. Once separate sights were used, the jacket could be dispensed with entirely, leaving the plain, skinny barrel protruding rather oddly from the bulky receiver. Despite these modifications, some Schwarzloses fitted to aircraft retained their cooling water jackets to the end of the war.

The M07/12 was found to be sensitive to changes in atmospheric pressure, firing more slowly and finally stopping when the aircraft climbed above an altitude of 10,000 feet. A set of modifications designed by Ludwing Kral raised the rate of fire to nearly 600 rpm and the critical altitude to almost 18,000 feet. Mid-way through the war, a version specifically for aircraft use was developed, the M16, in which the weight was reduced to 29 pounds. Continued development eventually saw the free rate of fire of the M16A increased to 880 rpm, and raised its operating altitude to 23,000 feet. But even in March 1918 fewer than 300 M16s were in service, and the M07/12 remained numerically the most important gun in the inventory.

By the middle of the war, it had become established that the most satisfactory layout for a fighter plane was the tractor type, with the engine in front of the pilot. This meant that if the guns were to be kept within reach of the pilot (important at that time, as guns often jammed and needed clearing), their firing needed to be synchronised with the engine revolutions so that the bullets passed between the propeller blades.

Most synchronisation systems needed to be tailored to the gun they were used with, and the Schwarzlose’s unique mechanism required a purpose-designed system. The most common seems to have been the Zaparka gear, which fired the gun on every fourth propeller revolution. The mechanism could be relied on only within a band of engine revolutions between 1,000 and 1,600 rpm with the M07/12, and 600 to 1,600 rpm with the M16. This explains the very prominent place given in the cockpit of fighters to a large engine tachometer. The 1,600 revolutions per minute limit restricted the maximum rate of fire to 400 rpm regardless of the free rate, and it would obviously have been less at lower engine revolutions. The Bernatzik and Daimler gear reduced the rate of fire even more, by 55% in the case of the M16. However, the Daimler gear did have the advantage that the M16 could be safely fired from engine idle to 1,600 revolutions per minute, although the M07/12 was still restricted to the 1,100 to 1,600 rpm band. None of these systems proved to be entirely reliable, leading to a loss of confidence in the pilots who risked shooting off their own propellers. At the end of the war the Austro-Hungarian forces decided to standardize on the Priesel system.

Aircraft installations

Aircraft used by the Austro-Hungarian Empire were a mixture of indigenous and German types. Some of the latter were specifically made for the Empire, and these were usually armed with Schwarzlose guns.

Synchronisation systems for the Schwarzlose were not available until 1916, so earlier fighters needed to find other ways to mount their guns. Among the first of the Empire’s fighters was the German-built Hansa-Brandenburg D.I, armed with an unsynchronised Schwarzlose in a fairing on top of the upper wing so it could fire over the propeller. This fairing was known as the VK canister. The standard version was the Type II VK, which held a gun and 250 rounds of ammunition, plus a gravity fuel tank, but sometimes two guns were installed in the canister. The Hansa-Brandenburg D.I was also built under licence by the Austro-Hungarian Phönix company, but this version did not prove very successful. The Phönix D.I combined its fuselage with new wings, a more powerful engine, and two synchronised Schwarzlose guns. It was a much better fighter, but deliveries started only in the spring of 1918. Very small numbers were delivered of the improved D.II and D.III. After the war, the D.III went on to serve with the Swedish Air Force. The other successful family of Austro-Hungarian fighters was entirely indigenous. The Österreich-Ungarische Aviatik Flugzeugfabrik (not to be confused with the German Automobil und Aviatik A.G., which also built a number of fighters) produced the Aviatik D.I, which in prototype form had a single synchronised Schwarzlose but entered service in the summer of 1917 with two.

In addition to these, the German Albatros D.II and D.III fighters were built in the Empire and armed with two synchronised Schwarzloses. Some Fokker D and E series were also used.

Despite its bulk, the Schwarzlose was also used as a defensive gun in flexible mountings. Single-engined two-seaters (known as the C class in both Germany and the Empire) which carried such armament included the German-built Hansa-Brandenburg C.1 (which also had a fixed gun in a VK top-wing canister for the pilot) and several indigenous designs from Lloyd, Lohner, Oeffag and Phönix. Thirty twin-engined German Gotha bombers were supplied to Austria, who fitted them with Schwarzlose MGs. Hansa-Brandenburg also supplied the W.18 floatplane, and the indigenous Lohner L of 1915 was a three-seat single-engined flying boat. Both carried one Schwarzlose gun.

While the Schwarzlose was not best suited to aircraft use, the Austro-Hungarian Empire engineers were able to make some remarkable improvements, which turned it into an acceptable aircraft gun.

Schwarzlose Technical Data

Length: ….. 42 inches Barrel length: ….. 20.9 inches Weight: ….. 43 lbs (M05, M07, M07/12), 29 lbs (M12, M16) Method of operation: ….. Retarded blowback Calibre: ….. 8x50R Mannlicher (except M12: 6.5×54 Mannlicher-Schönauer) Ammunition feed: ….. Cloth belt Cyclic rate of fire: ….. c.400 rpm (M05, M07, M12), c.500-580 rpm (M07/12), c.600 rpm (M16), c.880 rpm (M16A)

(Anthony G Williams is co-author (with Emmanuel Gustin) of “Flying Guns – World War 1: Development of Aircraft Guns, Ammunition and Installations 1914-32”, published by The Crowood Press in 2003. You can visit him at www.quarry.nildram.co.uk)