As other installments in this series show, there were already significant issues with the first few iterations of the new prototype “Small Arms of the 1980s” (SA80) family of weapons. From an initial concept in 1971, these had seen 8 years of development by the time they emerged from NATO ammunition trials in 1979. At this time, the initial emphasis on building these weapons in a new British caliber, the 4.85x49mm cartridge, shifted, and the 5.56x45mm chambering came to be accepted. The internal project name became “Enfield Weapon System,” rather than the earlier “485 Weapon System,” in a tacit recognition that 4.85mm was effectively dead. The caliber was not the only casualty, however, as the weapon itself was about to be radically redesigned. RSAF Enfield lacked experience in the design and especially the manufacture of contemporary firearms, and the definitive XL64E5 IW (rifle) and XL65E4 LSW (LMG) had shown serious problems with functioning and excessive barrel wear. They had been expected to achieve a mean rounds between failure (MRBF) rate of 2500 MRBF for the IW and 8000 for the LSW. The early figure after the NATO trial was exceptionally low, at just 97—indicating weapons unfit for military service.

Tackling the Issues

The issues which resulted in this poor performance could no doubt have been resolved; these were, after all, prototype designs that had yet to pass through Ordnance Board, “user” and troop trials. The coincidence of the NATO ammunition trials was unfortunate timing in that it interrupted development, but at the same time it was an opportunity to spot serious issues early on and rectify them before formal British trials began. The design was promising enough, and the need for a new British rifle and machine gun urgent enough, that it was decided to move ahead with the next developmental iteration. Unfortunately, before any individual issues with the original design could be tackled, the cost of production was deemed to be too high and a second round of “value engineering” (VE) was demanded. This was supposed to be a refining of an already proven and functional design to make it more economical to produce. The first VE study had changed minor details like the shape of controls or individual contours of the receiver. Yet only 4 years after the original weapon system had been launched, the findings of this new study resulted in a substantial and visually obvious redesign; practically a new gun (the subject of this piece). This “reset button” approach only compounded the factory’s existing difficulties, with the original targeted in-service date (ISD) of 1983 just a few years away.

Embracing Feedback

Embodying the value engineering feedback, another short run of prototypes was produced; this time just three rifles with serials prefixed “PR” for “Production Rifle.” The new design was much bulkier and more wedge-shaped compared to the svelte XL60 (superficially it is very close to the final SA80 design). As a result, weight increased; unfortunately, due to the VE focus on cost-saving, quality did not. In fact, with limited experience of pressing and weld-ing, and morale increasingly an issue, quality control was variable from this point until the closure of the Enfield factory in 1988.

Nonetheless, the design itself had issues beyond this. The new pressings were thin and easily distorted, despite the new rifle weigh-ing a full kilogram more than the XL64E5. The new trigger mechanism housing (TMH) was also found to be insufficiently strong to support a loaded magazine. The TMH mag-azine well was a short, lipped design just a few millimeters tall. The trigger mechanism was also substantially redesigned, and the safety reverted to a cross-bolt type in an effort to minimize inadvertent operation by left-handed users. This allegedly became critical much later on when the final L85A1 was in service, as the polymer catch—chosen on cost-saving grounds—swelled with envi-ronmental changes and became difficult to operate. The SUSAT, still in prototype stage, was given a new mount, operated by a single throw lever. For now, these guns carried over the existing mechanical design of the XL60 series, with the exception of a new bolt design incorporating double ejectors and a more conventional (longer and narrower) AR-style extractor, no doubt both attempts to improve the weapon’s reliability. More changes were to come in the definitive XL70 series, however.

Design Changes

The most obvious change in this next, much longer production run of prototypes was the incorporation of a longer, separate external magazine well assembly. This was seam-welded onto the bottom of the existing TMH. A thick and heavy piece of sheet metal was introduced to contain the trigger group as a drop-in assembly. This had a vertically ribbed reinforcement at its front which served as a guide for the rear aspect of an inserted magazine (i.e., it formed the back of the magazine well). A sheet metal hammer stop was welded to this new trigger group assembly. The bolt carrier was of yet another new pattern, being substantially wider and sporting simplified lightening cuts on both sides. Apparently bolt bounce had been addressed in some way, because the inertia pellet was eliminated; its channel being enlarged and bored clear through in order to accommodate the new guide rod. Contrary to claims in Steve Raw’s The Last Enfield, the dual ejectors on the “PR” bolt were deleted and never seen again.

The slender twin guide rods and springs taken from the AR-18 were replaced by a stronger (and therefore heavier) triple rod design. This replaced the twin springs with a single spring fitted to the larger central rod, leaving the two outer rods to function simply as bolt carrier guides. This allowed the internal guide channel in the body (upper receiver) to be reduced to a simple ledge—serving only to keep the cam pin in the down and unlocked position until the bolt was in battery—and the corresponding guide peg on the bolt carrier to be eliminated, simplifying the design. The cocking handle was slightly altered into what would become the standard A1 pattern. In an example of detailed value engineering, the machined orienting/locating lug on the handle was replaced with a simple roll-pin (a simple and effective arrangement that persisted into service).

The gas system components were slightly redesigned to reduce the complexity of machining operations. The spigot formerly machined into the gas cylinder was eliminated, as was the hollowed nose of the operating rod. Instead, the gas cylinder was hollowed at both ends to accept the piston/gas plug at the front and the rod to the rear. This raises another interesting divergence from the AR-18. The XL60 had already simplified the ArmaLite four-piece gas system to three components, without a connecting link (still to be found in other derivatives, including the German Heckler & Koch G36 design). This link was deemed superfluous, having apparently been included simply to ease disassembly. The XL70 took the design another step further from the original, employing a simple tubular gas cylinder. Finally, the design also returned to a rear sling loop mounted on the rear of the body. The flash-hider was now standardized on both variants but altered to use radial lines of circular ports (three in each row) rather than slots.

A wholly new set of dark green polymer furniture was designed, of essentially the same pattern as would eventually enter service. The handguard was fully developed with a polymer cover over the sheet metal upper guard and a metal heat-shield liner in the lower. The buttplate was now polymer, with a steel sling loop inserted. The plate wrapped around the toe of the butt as per the A1, but here it was of hard polymer rather than rubber. The pistol grip shape changed slightly, retaining a storage compartment. A new cheekpiece was, as before, simply glued directly onto the receiver. The new bolt release catch and the action dust cover were in matching green polymer (and are as per the A1 in design), but strangely the hold-open catch is black.

The SUSAT was also redesigned by this time and had received the designation XL9E1. This version eliminated the auxiliary grenade sight bracket from the body casting, no doubt to reduce the weight of this hefty optic design. Another new mount, operated by means of two wing bolts and a spring catch, was carried through onto the in-service rifle.

Common Traits

As before, the LSW shared much in common with the IW aside from its heavy barrel and bipod. It retained open-bolt operation but, in another attempt to simplify things, the engineering team did away with the Stoner 63-style main and auxiliary sears, and the gun now operated in open-bolt fashion regardless of semi-au-tomatic or automatic mode. This slam-fire, fixed firing pin design required that a safe position be added to the change lever (fire selector) to prevent accidental discharge if dropped with the bolt carrier locked to the rear ready to fire (regardless of the trigger safety). There being no closed-bolt mode of operation, the safety (auto) sear was deleted from the trigger group. This decision ran counter to the idea of maximum commonality of parts, since this version therefore required a unique carrier design not interchangeable with the rifle variant. The hold-open catch was also flipped around.

Early examples in the XL70 series, like the XL73E2 LSW (pictured), feature a set of black polymer furniture, including an XL60 pistol grip, an unusual cheekpiece that conforms to the shape of the receiver (rather than being smooth) and a buttplate of a unique oval pattern not found on either the XL60 series or the later XL80. Early IW handguards were as per the XL70E3 shown here, but in black. The equivalent XL73E2 handguard is roughly the same shape as the service version, being shorter and with a hand-stop moulded in at the front. It also has a heat shield; however, the prototype form shown here is roughly made and lacks the thin finger-stop of the rifle equivalent. The bipod is non-adjustable and, as currently installed, no longer unfolds. These early guns look and feel more like prototypes than those in the green furniture. Inside, parts of the trigger mechanism look hand-finished, and the trigger pull on this open-bolt-only gun is abysmal.

And Then There Were Three

At this stage, the requirement for a left-handed LSW was dropped, reducing the number of variants in the family to three. The three PR weapons (all IWs) were chambered in 4.85x49mm, but the decision had already been made to move to 5.56x45mm, and the first of the true XL70 guns were fitted with 1/12 twist barrels and chambered for US M193 ammunition. Nonetheless, the need to move to 1/7 to suit the SS109 cartridge was already anticipated. Whereas the PR guns had been left without “XL” designations, these new weapons were named as follows:

XL70E3—Individual Weapon
XL78E1—Individual Weapon (left-handed) XL73E2—Light Support Weapon
NB, in terms of nomenclature, “rifle” and

“machine gun” persisted in use alongside “IW” and “LSW.” The term “PW” (personal weapon) was also used, in place of IW.

Trials of the XL70 series began in earnest the following year (1981), in an effort to keep the project on schedule. Enfield had suspected in 1972 that it might take until 1984 for full-rate production to be achieved, yet in 1975 they agreed to an ISD of 1983. In an effort to meet this, it is alleged that corners were cut and standards kept artificially low during the trials process. In particular, it is claimed that chicanery played a part in the weapons being seen to meet the required MRBF. Certainly, the new design had inherited some existing issues, along with all-new problems (such as failure to lock open on an empty magazine). The XL60 series had suffered from excessive barrel wear due to a combination of poor metallurgy and a lack of chrome lining (incidentally, this marked the first time that the German firm of Heckler & Koch would be consulted, more than 20 years before the A2 programme). However, metallurgy and inadequate heat-treating continued to plague the weapon, with cracked bolt carriers and even a split barrel revealing serious defects in the manufacturing processes. These catastrophic issues were resolved following Phase A of the User Trials but were a worrying sign at this advanced stage. Prior problems with feed, ejection and trigger reset that had been experienced with the XL60 series remained evident, as did the LSW-specific problem of split groups. This was specific to automatic fire with the LSW, wherein the weapon would produce two discrete groups—the first shot exhibiting a distinctly different point of impact than the remaining shots in a string. This would be the subject of significant work in future iterations of the LSW (stay tuned for more on this issue—Ed.).

As User and Ordnance Board trials continued in parallel, the weapon was able to reach the target 2500 MRBF figure despite these problems. If this seems low by today’s standards, it is important to note that at this period, U.S. military rifles might only be expected to reach 500 rounds more (i.e., 3000 MRBF) than the SA80 IW target for the equivalent failure category. It is essential to point out that, in the British trials, the only categories of failure included were those that involved a malfunction requiring user replacement of parts. Other commonly tested failure modes, namely malfunctions that could be solved with more intensive user intervention (but not parts replacement) and those remedied by immediate action alone (sometimes referred to as “mean rounds between stoppages,” or MRBS) were—according to Steve Raw—ignored. On the other hand, the contemporary U.S. military demanded an MRBS figure of 500, whereas the XL70 SA80 achieved only 95 MRBS. In other words, the weapon on average would malfunction after only three full magazines. Even if the weapon achieved its set MRBF target, an MRBS rate such as this could not possibly be acceptable in service. This worrying situation led to yet another build standard and yet another designation, which we will deal with in the next installment of this series.

Special thanks to the National Firearms Centre at the Royal Armouries, who graciously allowed us access to their world-class collection.
This is Part 3 in a series of articles examining the developmental history of the United Kingdom’s SA80 family of firearms. Part 2 appeared without designation in Small Arms Review, Vol. 23, No. 3.
See armamentresearch.com for further original content.
(This article is adapted from a chapter in Mr. Ferguson’s forthcoming book on British bullpup rifles, which will be published by Headstamp Publishing in 2019. HeadstampPublishing.com)

After successfully evolving from the XM16E1, the Colt M16A1 rifle, adopted during 1967, continued in service until 1983. Despite the rifle’s problematic beginning during the Vietnam War, it evolved into a world-class military weapon, and its 5.56mm cartridge has become the NATO standard. 

The origins of the M16A2 rifle began with a request from the U.S. Marine Corps, who pride themselves on marksmanship and a tradition of “Every Marine a Rifleman.” During September of 1979, Marine Corps representatives met with Colt to discuss their ideas on how to improve the M16A1 rifle. They wanted a rear sight adjustable out to a range of 800 meters, a more accurate cartridge, and one that could penetrate military helmets and body armor at 800 meters. The Marines wanted a 3-round burst feature in place of the full-automatic function. During training, the Marines were hard on their weapons, particularly during bayonet drills. In order to have their rifles stand up to rough use, they requested a heavier barrel, and more durable plastic stocks and forearms.

The Joint Services Small Arms Program approved a rifle evaluation program and ordered fifty Product Improvement Program (PIP) M16s. The updated rifles were assembled on M16A1 lower receivers and designated as M16A1E1 rifles. These modified weapons were tested by U.S. Army and Marine Corps personnel. The Marines were enthusiastic about the M16A1E1’s enhanced performance, and it was type classified as the M16A2 rifle during September of 1982. It was adopted as the Standard A rifle in November 1983. The Marine’s initial order was for 76,000 M16A2 rifles, and the first delivery went to their Marksmanship Training Unit in January 1984. The U.S. Army, whose marksmanship training was different than that of the Marine Corps, was less interested in the new rifle and had plenty of serviceable M16A1 rifles in their inventory. That said, the Army ordered their first lot of M16A2 rifles in 1986.      

As adopted, the M16A2 rifle had several new features, some of which proved to be controversial. The features implemented into the PIP M16A2 included:

• A three-round burst, replacing the full-auto function
• Case deflector for left-handed shooters
• A new flash-hider / muzzle brake
• Barrel with 1:7 twist to stabilize the M855 and M856 cartridges with the longer, heavier bullets
• The diameter of the barrel was increased from the rear sight base to the muzzle
• Rear sight adjustable for elevation and windage
• Square front sight post
• Interchangeable handguards
• Longer buttstock with new buttplate
• Pistol grip with finger rest
• Tapered slip ring
• Round forward assist plunger
• Receiver reinforced at the rear area and the front pivot pinhole

Critics

Not everyone was happy with the updated M16A2 rifle. Complaints were that the 3-round burst was not resetting. In other words, if one shot was fired, the next trigger pull would only fire two shots; if two shots were fired, the next trigger pull would fire one shot.

Older M16A1 rifles with their barrel’s 1:12 twist rate could not stabilize the new M855 round and the M856 tracer round with their heavier and longer bullets

The new adjustable rear sight was considered overly complex for a combat weapon. The Marines, who requested the new rear sight for the M16A2 trained differently than the other services, particularly the Army whose evaluators were not as receptive to this change. Canada adopted the M16A2 as the C7 but retained the M16A1 upper receiver with the less complicated rear sight.

The M16A2 rifle has a loaded weight of 8.8 pounds, which is nearly a pound heavier than the M16A1 at 7.9-pounds loaded. Most of the weight increase is due to the M16A2’s heavier barrel.

In 1989, kits were made available to upgrade M16A1 rifles remaining in inventories to the M16A2 configuration. Handstamps were used to mark the receivers signifying the upgrade. The kits included: the M16A2 rifle’s barreled upper receiver, burst trigger group, buttstock, pistol grip, and handguards. These kits were supplied to the U.S. Military by several contractors.

The M16A3 Rifle

The M16A3 variant was simply an M16A2 that had a full-automatic feature in place of the 3-round burst. Very few were manufactured and issued.

The M16A4 Rifle

From the very beginning, the AR-15/M16 series of rifles featured an integral carry handle. This was a necessary design feature because the buttstock was in line with the longitudinal axis of the barrel’s bore, increasing controllability during automatic fire. However, the height and placement of the carry handle required the rear sight to be elevated. Additionally, this handle design made it difficult to adapt any type of newly developed, modern optics to the rifle. To solve this problem, the M16A4 was introduced in 1997. The M16A4 model had a flat-top upper receiver with a Mil-Std-1913 rail. Initially, the upper receiver had a detachable M16A2 carry handle that was secured with thumbscrews to the rail. The handle could be easily removed, and the rail used for mounting optics and other ancillary devices.

The 3-round burst feature of the M16A2 was retained in the M16A4 design. Eventually, the original round handguards fitted to the M16A4 rifle were replaced by the M5 Rail Adapter System from Knights Armament, providing a solid platform for the attachment of additional equipment. In 1997 the M16A4 rifle began replacing the M16A2 as the standard rifle of the U.S. military. Both rifle models were manufactured by Colt and FN.   

The M4 Carbine

The M4 and M4A1 carbines, initially adopted in 1994, became the U.S. standard issue weapon replacing the M16A2 and M16A4 rifles. These compact carbines feature a 14.5 inch barrel and a collapsible buttstock. In 2012, the Army began procuring the M4A1 variant and issued a Modification Work Order (MWO) to upgrade existing M4 carbines to the M4A1 configuration. The M4 has a 3-round burst feature, while the M4A1 has gone back to having a full-automatic function. The M4A1 also has an ambidextrous selector and a heavier barrel.      

The Colt Factory Strike

Colt employees were Members of United Auto Workers Local 376, they walked off the job on January 24, 1986, after working 10 months without a contract. The strike officially ended four years later, on March 22, 1990, with the announcement of a buyout agreement that made Colt employees co-owners of the plant, along with managers, the state of Connecticut, and private investors. During 1988, while the Colt employees were on strike, Colt lost their M16 contract to FN.

FN M16A2 Rifles

In 1988 the U.S. Government awarded a $112.1 million contract to a Belgian firm to produce 266,961 M16A2 rifles over five years. Under the new contract, the M16A2 and M16A4 rifles would be made at Fabrique Nationale Herstal’s (FN) manufacturing facility in Columbia, South Carolina. FN Manufacturing confirmed that their bid of $420.00 for each rifle (compared to Colt’s bid of $477.50) would save the government approximately $15.3 million over the life of the contract. Many of Colt’s patents on the rifle expired in 1983, but a licensing agreement with the United States Government permitted the Army to give technical data on the weapon to other manufacturers. Both the U.S. Army and Colt Industries, inc., announced the change had resulted solely from Colt’s being underbid by FN, and that it was not related to the quality of Colt rifles, or the strike by Colt workers in Hartford.

Other M16A2 and M16A4 Rifles

In addition to FN and Colt, M16A2 and M16A4 receivers and rifles were manufactured in small numbers by other companies.

Sabre Defense LLC

During July of 2008, Sabre Defence of Nashville, Tennessee was awarded a U.S. Government Indefinite Delivery/Indefinite Quantity (IDIQ) contract for 4,952 M16A3 and 702 M16A4 rifles to support the U.S. Navy, U.S. Marine Corps, and foreign military customers. Sabre joined Colt and FN as the third company chosen to manufacture M16 rifles for the government since the weapon was adopted.

In February of 2010, federal agents raided Sabre Defence’s Nashville, Tennessee facility. Several company executives were charged with illegally exporting firearm components and other defense items. The accused admitted to concealing Sabre’s illegal exports from 2003 until 2009, using falsified shipping documents and shipping crates with false bottoms. Sabre maintained a fictitious set of business records to conceal its unlawful shipments of firearm parts. Unable to recover from the incident, Sabre Defence declared bankruptcy and went out of business in 2013. Very few Sabre M16 rifles were delivered to the U.S. military.

Balimoy Manufacturing

The Balimoy Manufacturing Company of Venice, Florida manufactured replacement receivers for M16 rifles. Most were originally marked as M16A1 with an AUTO selector position. The A1 model was over stamped A2 and the word AUTO milled out and re-stamped BURST. The receivers were marked: MFR 2U894, Property of U.S. Govt’ BALIMOY MFG CO
VENICE, FL. During a program to rebuild and update M16A1 rifles to a M16A2 configuration, the U.S. Anniston Army Depot used Balimoy M16 receivers to replace original receivers that were rendered unserviceable.  

Transferable M16A2 Rifles in the NFA Registry

Fortunately for the NFA world of enthusiasts, a small number of Colt manufactured M16A2 rifles made it into the registry before the 19 May 1986 cut-off date, which ended the registration of transferable machine guns. Most of the available M16A2 rifles were those made for the export and police market, the serial numbers documented were in the 8,000,000 range. However, there were a few U.S. Gov’t Property marked M16A2 rifles that made it into the system, allegedly registered by John “K”, a somewhat mysterious individual from Pennsylvania.  To date, there have been 35 documented serial numbers of transferable U.S. marked Colt M16A2 rifles in the NFA registry. Manufactured during 1983-1986 these serial numbers are in the six-million range. John “K” was reportedly also involved in procuring a number of H&R M14 rifles, and US Gov’t Property marked M16A1 rifles from Harrington and Richardson’s asset reduction sale in 1985.

Most of the transferable Colt M16A2 rifles manufactured for the commercial market which made it into the NFA system were assembled with full-auto capability, and the selector position marked AUTO. Meanwhile, most of the U.S. Property marked M16A2 rifles were fitted with the U.S. military designated 3-round burst feature; the selector position marked BURST. However, the 3- round burst can easily be converted to a full auto function by simply replacing the trigger group, the same applies if a 3-round burst feature is desired. Due to their smaller numbers, M16A2 rifles generally sell for a higher price than the more common M16A1 model.   

RECOMMENDED READING

Black Rifle M16 – Vol. 1 & 2 by Christopher R. Bartocci, R. Blake Stevens, Edward C. Ezell
Vickers Guide: AR-15 by Larry Vickers, James Rupley

The AAI ACR, a modified version of the previous AAI SBR rifle, as it appeared in the ACR field experiment. This rifle fired a 5.56x45mm subcaliber flechette round at 4,600 fps, at a cyclic rate of 1,800 rpm in the three-round burst mode. (U.S. Army)

By R. Blake Stevens

“Reorienting” the SPIW and Adopting the XM16E1

Again, as had been the case in 1964, the most charitable conclusion after the second generation SPIW trials was that neither of the “weapon concepts” was acceptable in its present state. The AAI SPIW was chosen as the better of the two: hardly a choice at all in view of the enforced termination of the Springfield program and the lack of any immediate civilian interest in its continuance.

Early in the fittingly gray month of November, 1966, the Infantry Board formally recommended to the Chief of Staff of the Army that the whole SPIW program be radically pruned back and relegated to the status of an exploratory program at AAI.

On November 7, the Office of the Chief of Staff accordingly directed that the SPIW program be “reoriented” from full-scale engineering development back to exploratory development, becoming in the process just one facet of a broadened, long-term small arms R&D program for the future. The same memorandum announced the formal intention to adopt the Colt XM16E1 rifle as standard for the U.S. Army everywhere but in the European theater.

With the Army having thus come full circle and now solidly behind the M16, the pressing need for the SPIW simply vanished. For the SPIW itself, the collapse of the second generation program marked the end of the lavishly-funded grande époque, the likes of which would never be seen again.

The AAI XM19 Serial Flechette Rifle (SFR)

Nevertheless, development continued at AAI over the next few years, funded largely from within the company. This led to a heady but temporary resurgence of interest in the flechette-firing SPIW.

The Army had seized on the limited but encouraging success of AAI’s 1967 nominal-fee contract modifications, authorizing an additional $500,000 in fiscal 1968 to step up produceability studies on flechette ammunition.

The Army’s new four-phase serial flechette rifle (SFR) contract with AAI became a reality in October, 1968. A field experiment had already been tentatively scheduled for April, 1970, wherein the new SPIW would be compared with the M16A1 under simulated combat conditions.

HQ Army Weapons Command (now called WECOM) publicly confirmed the awarding of the letter contract to AAI on January 21, 1969, “for continued development of the Special Purpose Individual Weapon (SPIW) and its associated ammunition.” A scant six months later in June, WECOM announced that the phase-two prototypes, now officially called the “XM19 Rifle, 5.6mm, Primer Activated, Flechette Firing,” were under construction. This first bestowal of an official “XM” number on a SPIW candidate was an important and long-awaited honor: it signified formal recognition that the SPIW had advanced one indispensable step closer to becoming the Army’s next rifle system.

Calling the SPIW to Account

If anything could have saved the SPIW program it was AAI’s improved XM19 rifle and its later, short-lived follow-on, the XM70, which fired from the open bolt. However, to an increasing number of observers, both in and outside the program, the curious and continued determination to ignore the fundamental gulf between the SFR (SPIW) requirements and the real world needed to be addressed. On July 30, 1969, Congressman Richard L. Ottinger of the House of Representatives wrote a formal letter to the Comptroller General of the United States. By this time, some aspects of the Future Rifle Program were already under investigation by the U.S. General Accounting Office (GAO). An excerpt from Mr. Ottinger’s letter reads as follows:

… I am writing in regard to the Special Purpose Individual Weapon (SPIW) currently being developed by the AAI Corporation for the Department of the Army… It is my understanding that after seven years of research and development and the expenditure of some $20 million, the SPIW is still not ready for production and use. I further understand that some five different engineering deficiencies have been identified and that it is anticipated that some additional 12 to 18 months will be necessary to correct these deficiencies.

I would appreciate your advising me as to how much more it will cost to correct the five present deficiencies and whether any additional research and development funds will be spent; why is this weapon being developed in the first place, [and] when will the SPIW be ready for use by our Armed Forces personnel?

The XM19 is Snatched from Near Perfection

Ironically, it appears that by this time the AAI weapon was virtually at the point of perfection, and yet as the XM19 neared this tantalizing goal its detractors gained in voice and power, and the mood of good fortune, which had begun in 1967, began to slip away, never to return.

Withdrawal from Vietnam Pulls the Plug on the SPIW

In the midst of all these acrimonious thrusts and investigations, the 1973 end of the American military presence in Vietnam effectively “pulled the plug” on any urgent, large-scale development plan for a new U.S. individual weapon. Small arms research, development and engineering (RD&E) money dried up abruptly, adding an indisputable air of finality to the last SPIW developments. As stated in the Research, Development and Engineering (RD&E) Laboratory Posture Report for fiscal 1974, prepared by Army Armament Command at Rock Island:

… In December 1973, the decision was made to remove flechette ammunition from immediate consideration within the FRS (Future Rifle Systems) Program because of technical problems which may not be correctable in the time frame of the future rifle…

Summing Up the Failed SPIW Program

The point target portion of the AAI SPIW was designed to fire controlled bursts of 10-grain flechettes at 2,400 rpm, thus taking advantage of the flechette’s minimal recoil to achieve a deadly, ultra-tight mean burst spread. As regards the crucial characteristic of recoil impulse, the 10-grain flechette still reigns supreme, far superior to the M16 on full-automatic fire. As recorded in The Black Rifle, a comparison prepared by the Human Engineering Labs (HEL) at Frankford Arsenal showing the typical recoil impulse of several standard weapons reads as follows:

7.62mm NATO M14: 2.65 lb. sec.
.30 M2 Carbine: 1.18 lb. sec.
5.56mm M16 (w/muzzle brake): 1.16 lb. sec.
AAI SPIW (no muzzle brake): 0.65 lb. sec.
AAI SPIW (w/muzzle brake): 0.39 lb. sec.

For such a light projectile to be lethal, however, a muzzle velocity in the order of 4,800 fps was required. This in turn necessitated a chamber pressure approaching 70,000 psi.

In the frantic attempt to perfect weapons capable of attaining these pressures and velocities, many frontiers of knowledge had to be pushed back, all at the same time. This in turn uncovered a veritable host of new technological problems that could not possibly have been foreseen and which, ironically, were misconstrued as poor engineering. It was the previously unheard-of magnitude of these new problems – heat; erosion; muzzle blast; component overstressing and flechette cartridge complexity – which ultimately proved insurmountable within the overall timing and funding constraints set for the program.

A Brief Reprieve – in the ACR Program

The following is excerpted from the Collector Grade title Black Rifle II, written by Christopher R. Bartocci and published in 2004 as a follow-on to The Black Rifle, which had covered the early history of the M16 up to the time of its publication in 1987.

We begin with an overview of, and rationale for, the Advanced Combat Rifle (ACR) program from Black Rifle II, as follows:

Throughout the last half of the twentieth century, the U.S. Department of Defense initiated several programs aimed at replacing the M16 series rifles altogether with a new design.

When the AR-15/M16 was first adopted during the early 1960s, it was considered merely an interim weapon while development of the futuristic, flechette- and grenade-firing Special Purpose Individual Weapon (SPIW) was under way. At that time it was confidently predicted that the SPIW would be classified “Standard A” by June of 1965. Despite a great deal of costly effort, however, the SPIW concept was never perfected.

Twenty years later, during the period 1986 to 1990, the Department of the Army tried again, by funding the Advanced Combat Rifle (ACR) program.

It had been a hard but valuable lesson to learn that, due to the high levels of stress, fatigue and fear experienced during actual combat engagements, soldiers will not shoot as well as they were trained to shoot. The objective of the ACR program was to replace the M16A1, and the then newly-adopted M16A2, with a new rifle, which would increase both hit probability and combat effectiveness by 100%.

Excerpts from a voluminous retrospective prepared by the Army Research, Development and Engineering Center (ARDEC) at Picatinny Arsenal titled ACR Program Summary read as follows:

“The ACR Operational and Organizational Plan (O&O) was approved in January, 1985 [which] caused weapon concepts to be developed under contract and prototype hardware to be produced and evaluated with troops in a field experiment.

“In September 1982 contracts were awarded to AAI Corporation and Heckler & Koch, Inc.
“In 1984 – 1985, industry conferences were held at ARDEC and Fort Benning. Shortly thereafter, contracts were competitively awarded to AAI, ARES, Colt, McDonnell Douglas, and Steyr [calling] for the development and fabrication of the proposed rifle systems for evaluation in government tests. Both the ARES and McDonnell Douglas contracts were terminated before the final ACR field experiment took place, due to “lack of maturity” of their systems.”

The AAI ACR

“AAI was the repository of the equipment necessary to produce the flechettes needed for both their contract and the Steyr-Mannlicher contract. The production of flechettes was a cost, time and quality problem throughout the entire development effort. There is some controversy as to whether the flechette round is inherently less accurate and whether any amount of future development effort would result in equal accuracy to a standard bulleted round. The pace of technology today is such that it is unlikely that further development work on small-caliber flechettes will be funded for rifles.

“The AAI weapon is a 5.56mm modified version of the previously developed Serial Bullet Rifle (SBR) using a reciprocating bolt mechanism.

“The AAI round uses the standard 5.56mm M855 brass case with M41 primer. The projectile is a 10.2 grain sub-caliber flechette. The sabot is a liquid crystal polymeric compound (plastic), which is designed in four segments held together by a neoprene “O” ring at the rearmost point of the sabot segments.”

The Steyr ACR

“The Steyr system was similar to the ARES system in that it fired using a rising chamber mechanism. However the Steyr ACR fired a single flechette from a plastic case using a radial ring primer. Initiation of the ring primer was from the side of the case near the base.

“The Steyr gun is a true open-bolt mechanism in that there is a spent case normally in the chamber in the out-of-battery condition. A live round only enters the chamber after the trigger has been pulled.

An inherent drawback to the Steyr system lies in sabot hazard to friendly troops. This is a safety concern that exists in the AAI system as well.

The Colt ACR

The Colt ACR was essentially a product-improved M16A2, painstakingly modified to meet the criteria of increased hit probability and combat effectiveness. It was fitted with a new hydraulic buffer, a modified pistol grip, a flat-top receiver with an integrated rail, capable of accepting a detachable carrying handle embodying the A2-style adjustable rear iron sight or the ELCAN (Ernst Leitz, Canada) optical sight, plus a heightened sighting rib proposed by the Army HEL (Human Engineering Laboratory) mounted on a semi-beavertail handguard, and a proprietary muzzle brake/compensator designed by Knight’s Armament Co.

Conclusions of the ACR Program -Reaffirming the M16A2

None of the ACR contenders emerged as a replacement for the existing arsenal of conventional rifles. However, the unprecedentedly sophisticated data collection systems developed for the program, which included the ability to not only record hits but to actually measure the amount by which a shot missed the target as well, led to some highly encouraging conclusions regarding the ACR contenders, plus an upwardly revised opinion of both the M16A2 and the soldiers who participated in the program. The following is a further excerpt from the ACR Program Summary:

… The baseline performance of the M16A2 rifle was better than anticipated in terms of hit probability… No rifles showed a n increase in probability of hit over the M16A2 under the stressed conditions of the test.

The feasibility of caseless and lightweight plastic-cased ammunition has more than been demonstrated in this program. Few problems were experienced with the [H&K] caseless rifles in the test. The past technical barriers of cook-off and vulnerability have now been overcome…

The End of the Road (So Far) for the Serial Flechette

A final excerpt from the ARDEC ACR Program Summary reads as follows:

… Many advances in high-performance rifle flechette technology have been made during this effort. New engineering plastics and sabot designs have solved previous launch reliability problems.
Although significant advances were made in reducing flechette round-to-round dispersion, the dispersion of flechettes is still greater than that of bullets. It is unlikely that the round-to-round dispersion will be reduced further, which would likely preclude flechettes from further consideration as single shot rifle projectiles.

[However,] their high cross-sectional energy density and large length-to-diameter ratio make them very effective against all small arms targets. This, together with their flat trajectory and short time of flight, make them attractive for consideration in crew-served and area-fire applications…

By Thomas T. Hoel, historical and technical editing by Dan Shea, Photos by Dan Shea

The operating system group is considered to be the heart of the M60 machinegun’s basic design, and it is here that the potential for the most common and expensive wear and damage within the whole weapon can occur. The operating system group consists of the operating rod, bolt group and the recoil/counter recoil parts. If problems with these parts, or improper operation of this group, are allowed to occur they can also greatly affect several other attendant systems within the weapon, primarily the barrel and the feed system and it’s components.

The kinetic motion of the weapon centers on the reciprocating movement of the operating rod, and the rotational action of the bolt assembly as it is driven forward and backward by the operating rod throughout the operational cycle. The bolt and operating rod are involved in a seemingly very simplistic relationship. But it is the inherently violent momentum of their interdependent movements that result in a host of wear-related problems that must be dealt with for continued reliable and safe operation.

Both the bolt and the operating rod are manufactured from high-grade ordnance steels, close-tolerance machined, stress-relieved and heat-treated to provide exceptional strength-to-weight ratios and resistance to wear and failure. Despite this, both parts will evidence clearly visible wear and deformation almost from the first time they are put into use. While it’s always unsettling for a new operator to discover these wear patterns, this is a natural occurrence and while it cannot be avoided, it can most certainly be mitigated. However, the fact that the gun quite normally “wears-in” new parts in this group, does not mean these parts should be ignored. If left unattended, these areas of galling and peening can produce dangerous stress concentrations, possibly leading to premature failure. As a consequence, all of the military manuals covering both operational field use and normal maintenance delve into this topic in great detail.

There are known locations within this system that generate wear. Together, the cam cut on the bolt body underside for the operating rod, the bolt locking lugs, and the cam ways in the barrel extension are designed to force the bolt body to rotate, both in locking and unlocking actions. The points of contact along these two camming surfaces are subject to greatly localized stresses, and will seek to spread this stress over a greater surface area. This action is what produces the visible areas of galling or peening visible on the bolt lugs, barrel extension cam ways (rare), and operating rod yoke (or yoke tower). This phenomenon was recognized early on, and several steps were taken to help alleviate the problem. The most noticeable modification was the addition of a roller bearing on the operating rod yoke, though more subtle changes were made in the angular diversion of the cam paths used, and a generalized increase in the contact areas of the individual components. If the formation, even if small in surface area, of galled or peened edges is observed, immediate corrective action is required to prevent continuing damage. Any evidence of galling or peened edges must be removed to restore the normal passage of lines of stress. There are three main locations within the system where this type of wear is observed.

First, examine the yoke tower of the operating rod along its frontal face, receiver guide ways, and the firing pin bearing channel. These surfaces essentially serve as forward and rearward travel limit stops for the bolt body at the end of its camming slot travel.

Conversely, the large mating surface area of the bolt camming groove located along the bolt body underside effectively spreads out any stresses within the bolt body there, and wearing of the sharp edges on this camming cut is unusual. Normally, a smoothly polished interior travel surface will be seen, with occasional evidence of slight surface deformation(s). In accordance with service publications such as TM 9-1005-224-23&P (or -24), visible surface burrs, gouges, or galling on the yoke tower and attendant firing pin bearing channel and receiver guide ways do not render the operating rod unserviceable, provided the damage is corrected by returning the surface(s) to a smoothly contoured area.

Experience has shown that on the yoke, the rear edges of the firing pin channel will evidence the most burring, directly above the firing pin roller bearing. (Note that the right-hand top edge, as viewed from the rear, is manufactured with a forward raked cut to the top edge; this is normal and reduces wear at this corner)

Use of the proper method for disassembly the bolt body from the operating rod yoke will greatly reduce operator induced wear during maintenance at the firing pin channel location, a major cause of premature wear here.

To correctly disassemble, invert the operating rod and bolt group, grasping the inverted top of the bolt body in the left palm, rear end facing away. While grasping the shank of the operating rod forward of the sear notch, apply pressure rearward against your left palm compressing the firing pin spring. Apply this pressure straight back until the yoke just starts to rotate…do not allow yoke to rotate. While holding the yoke firmly against rotation and firing pin spring tension, lift the forward end of the operating rod gently upward, carefully allowing the front edge of the firing pin channel to come up out of the bolt camming slot, and then slowly ease the firing pin forward to clear until it stops. Do not allow firing pin to snap forward. Done properly, neither the yoke tower or bolt body will slip out under pressure of the firing pin spring, which often times will cause gouges or burrs to form if allowed to happen. Reassembly is performed by reversal of these steps.

The second area to observe is the bolt head, and its locking lugs (and cartridge feed lug). These areas, in conjunction with the cam ways in the barrel extension, are the most stressed in the group as they bear the full intensity of the firing pressures of the cartridge. These areas encounter the brunt of the horizontal and rotational shock during bolt locking and unlocking actions as contact along these points is what starts and stops the violent rotation, and subsequent linear movement, of the bolt assembly in each direction of travel. These lugs will usually show more signs of wear than the corresponding cam ways in the barrel extension, and will be where the most attention must be directed in terms of preventative maintenance actions taken by careful removal of burrs or peening. Even more so than with the operating rod yoke, extreme care must be taken here when correcting any wear to make absolutely sure no lug contours are changed or excess material removed as safety of the locking action can be compromised. The top locking lug also forms the cartridge feed lug (cartridge stripping lug), and as such has significantly less material to start with than the lower locking lug. The top lug should always be given the closest scrutiny for any possibility that the incurred damages might not be removable by normal corrective action(s), without altering the underlying strength of the lug. The common wear pattern observed on the lugs is for the frontal surfaces to evince galling or slight burring around the sharp edges of the lug(s) where they travel in the cam ways of the barrel extension. Again, in accordance with service publications such as TM 9-1005-224-23&P (or -24) these minor deformations of the frontal surfaces of a particular lug are not cause for rejection of the bolt body as long as these areas are returned to a smooth contour.

The most severe damage that can occur to either the bolt lugs or barrel extension cam ways is in the form of cracking or chipping. Heavy gouging or deep indentations formed in this area will almost always lead to incipient cracking, and evidence of this type of damage is cause for an immediate inspection for integrity and subsequent rejection of the component. The equivalent problem may be observed along the exterior edges of the barrel extension cam ways. If any evidence of cracks, incipient cracking, or chipping, is determined to exist on the surfaces of the cam ways, a full inspection of the barrel extension (cam ways) is also immediately indicated. The only safe method for proper determination of any cracking suspected in the above areas is to subject the area to a fluorescent dye-penetrant test (with equivalency to MIL-I-25135), or MagnaFlux(r). (Virtually all aircraft service and repair shops will be able to offer these inspection procedures). If such an inspection procedure is unavailable, the only safe recourse is to replace the suspect part.

For all other cases of correctable repair, the proper remedial action is to carefully restore to a smooth surface the sharp edges of any galled, burred, or peened area by stoning with a fine grit polishing stone, without altering the basic underlying contour of the area. When using this technique great care must be taken not to alter or remove any of the underlying material, but merely to smooth out and remove the tiny displacements. (Never use a coarse grit stone or highly abrasive compound. 800 grit is an ideal basic) A final polishing of the affected area is recommended. Once these initial wear-in displacements are corrected, additional stoning is usually not required. However, if any of these components are changed, were-in problems may again arise. This may also occur if the firing pin or operating rod roller bearing are replaced. In rare instances, the spools of the firing pin may exhibit wear, which is, in turn, indicative of excessive wear of the firing pin channel edges. A damaged yoke roller bearing will cause excessive wear patterns on the inside surface of the bolt camming cut in the bolt body. It is therefore prudent to monitor these areas as well for additional signs of galling, burring, or peening, if any of the component parts of the operating system are exchanged.

The operating rod both retains the bolt and helps to cause it to rotate by a camming action as it is driven back and forth. The bolt is also supported and guided in its reciprocating movement by the feed-cam actuating roller, which is supported by the two bolt guide rails that form an integral part of the receiver. The gas tube, lower receiver operating rod supporting rail, and the bolt guide rails are the primary vertical support members for the operating rod and bolt assembly. Smooth and unbinding free movement along these paths of support is critical for correct functioning of the bolt and operating rod. It is always recommended to inspect these areas first, if wear begins to appear on either the operating rod tower or the bolt lugs. A simple lack of proper lubrication can cause excess drag along these supporting areas, which may lead to sluggish operation of the weapon in general, or failure even to fire a chambered cartridge. Lubrication of the operating group and its supporting components is critically important.

For virtually the entire military operational use of the M60, there have only been two normally approved MIL-SPEC lubricants, LSA and CLP. LSA (Lubricating oil, Semi-fluid, Automatic weapons, MIL-L-46000B) is a medium weight lubricating fluid, actually an emulsified mixture of multi-grade lubricants designed to provide effective lubrication protection over a wide range of atmospheric and temperature extremes. LSA was approved for field use in virtually all small arms in inventory and is a substantially effective general weapons lubricant when used in areas appropriate for its composition and formulation. Due to its chemical composition, LSA stocks that have been allowed to sit idle for any length of time will drop out of emulsion; to restore the lubricant to its full specification the mixture must be vigorously shaken, by mechanical means preferably. (To restore small quantities, individual containers can be heated in boiling water for a short period, or placed in a microwave oven set on Low for several seconds, and then shaken by hand.)

Standard M60 GPMG gas cylinder. This one is particularly nasty and came from a very old barrel that hadn’t been cleaned since the Stratford Hollow shoots, left in the back of a travel box. Note the scale and carbon build up, that made it necessary to drive the piston from the system with a rod and hammer. This is a prime example of a piston that would not slide when the barrel was tilted. It is not, however, beyond saving. Some good old fashioned cleaning solvent and scrubbing, and it will be usable again.

CLP (Cleaner, Lubricant, Preservative, MIL-L-CLP) was adopted to address what were considered to be shortcomings when maintaining weapons with the previous standard combination of LSA and RBC (rifle bore cleaner, MIL-C-372B or C). CLP is a complex formulation of cleaners (powder solvents), synthetic and natural lubricants, and anti-rusting and anti-corrosive (anti-acidic) compounds. While touted as a miracle formulation, CLP in general and widespread use has proven to be less than satisfactory for any of its intended uses. Its primary value as a weapons lubricant is dependent upon micro-grannular deposition of DuPont™ Teflon® (a fluoropolymerized lubricant) particles carried in suspension. When proper deposition of these minute particles occurs in the grain structure of a treated metal surface, the resulting lubrication properties are phenomenal. The main problem has been that successful Teflon® deposition rarely occurs and the remaining petroleum-based carrier fluid is not an effective lubricant, leaving much of the weapon unprotected from accelerated wear. It is mandatory that bulk concentrations of CLP be thoroughly agitated before use to efficiently distribute the Teflon® particulates in uniform suspension. For maximum Teflon(r) adhesion and deposition, the area(s) to be treated must be cleaned down to the bare metal surface with no trace of prior lubricants or preservatives remaining. Additionally, CLP does not achieve its’ maximum potential lubricity without numerous, long-term, continued applications.

Both LSA and CLP have their places and can be used effectively, although LSA is a far better choice for general lubrication of small parts if thorough cleaning and complete re-lubrication cannot be accomplished after every shooting session.

Neither LSA nor CLP are the best lubricants for several locations on the M60. On small parts, with small surface contact areas and low operating contact pressures, they are sufficient, but for large contact areas under heavy pressures another lubricant type is preferred for civilian use of the weapon.

Just as was found with long term experience with the .30 M1 Garand, .30 M1 Carbine, and M14 rifles, the use of any lubricant other than a heavy weight, high viscosity, grease for the bolt and operating rod contact areas led to immediate and disastrous problems. These critical parts often “froze” when used with lightweight lubricating fluids, even in ideal atmospheric conditions. The similarity of the operating components of these weapons to the operating system in the M60 suggest the same lubricant choice in certain highly stressed areas such as the operating rod yoke, bolt camming cut surfaces, bolt locking lugs, barrel extension cam ways, bolt and operating rod guide rail slots, feed cam actuator roller, and feed cam lever. The benefit of using such a high viscosity, extreme pressure, type of lubricant on these areas is that even under extreme operating conditions the lubricant will tend to stay where it is needed, continuing to provide vital lubricity.

The military standard for such applications is the unsurprisingly named MIL-SPEC lubricant, Rifle Grease (Grease, Rifle, MIL-G-46003 (ORD) Amend. 2). GI Rifle Grease is a high-grade, high-viscosity, temperature-stabilized, all-petroleum base lubricant with exceptional qualities for extreme pressure use and is formulated with anti-rust and anti-oxidant properties. While no longer a MIL standard lubricant, it is widely available as surplus stock. If GI Rifle Grease cannot be found in sufficient quantity for cost-effective use, it is also acceptable to use a more modern substitute. These products should conform to NLGI No. 2 multi-purpose applications, and will usually be found as a lithium-12 hydroxide base, molybdenum disulfide bearing, and extreme-pressure grease, such as generic automotive “wheel bearing grease.”

Liberal, but careful, application of this type of high-viscosity lubricant will provide long-term benefits significantly greater than if the weapon is maintained solely with CLP, LSA or other lightweight lubricants. Synthetic weapons lubricants such as MilCom TW-25B, and other such purpose-designed lubricants, are excellent for general use on the components of the M60, for those weapons in military use. However, civilians are not bound to consider all the same operational considerations as a military user, and use of the high-viscosity greases are more beneficial on certain components.

The last area of the operating system we need to consider is that part of the operating rod group that interacts with the fire control mechanism and counter recoil components.

The firing mechanism of the M60 is a relatively basic and straight forward design employing a simple spring loaded, single form sear which acts in combination with another simple machined cut on the underside of the operating rod. The sear is pulled into or out of engagement with the sear-cut on the operating rod by mechanical action with the movement of the trigger and its spring, and the sear spring. At least, that was the intention of the design. In use, however, the firing mechanism has two idiosyncrasies that must be understood and examined. The following applies to any variant of the basic design, and although with the M60D aircraft weapon variant the trigger is replaced with a linkage and trigger bars, the actions involved are exactly the same as in the ground guns.

The sear engagement surface cut on the operating rod underside is neither overly large, nor particularly aggressive, in its engagement with the sear. This has led to a reasonably accurate branding of the weapon as being prone to experiencing “run-away” operation. While the inherent design does indeed play into it, there are a few things the operator can do to prevent the situation from happening. As a relationship of the way the sear is forced to engage and hold the operating rod to cease firing, the operating rod sear engagement cut is placed under considerable impact loading which can over time cause the face angle to distort, lessening the available engagement contact area. This may continue to the point that the mere impact of the operating rod hitting the sear nose will cause the face on the rod to simply jump over the sear nose allowing the gun to fire additional rounds. The successful engagement of the sear with the rod face is dependant upon the nearly perpendicular mating of the two surfaces, any proclivity for either face to lessen that angle of contact through damaged contours, may be enough to prevent the trigger mechanism from holding fast the operating rod. While a certain amount of this distortion is unavoidable, the greater part of this wear is unnecessary. The most important thing any operator can do to prevent wear of these surfaces is to control the trigger mechanism in such a way as to prevent the two surfaces from experiencing “casual contact” as the gun operates. “Casual contact” occurs when the operating rod sear notch comes into partial contact at any point with the sear nose. This will inevitably cause frictional wear and low-level impact loading, forming galling or peening of the top edges of these surfaces, and greatly increasing the tendency for a run-away. For the sear nose and operating rod to function with the least amount of contact wear, they must never be allowed to contact each other, except when placed into sudden, full and complete engagement. Too often operators will not fully activate the trigger, allowing a small portion of the sear nose to continue projecting into the path of operating rod as it cycles. The gun will fire in this condition, but accelerated wear of the firing control parts is guaranteed also. The give-away is to view the underside of the operating rod and see if there is a polished track along its bottom edge. There should only be evidence of contact at the sear engagement notch, and nowhere else. If a polished track is present, the sear nose, via the trigger action, was not being pulled down out of the way. Again the correct remedial action is to restore these surface faces and remove the damage, without altering the underlying angular relationships of the base contours. Past a certain wear point, this may not be possible and replacement of the component may be required.

On the other end of the firing control spectrum is another problem that may result in a run-away gun. The sear must rise forcibly into the path of the operating rod in order to engage and hold the rod to stop firing. The sear is under spring pressure to provide upward vertical travel of the sear nose. In order for the trigger pressure to be within acceptable limits (trigger pull should be tested to be within a 6.0 lbs minimum, 11.5 lbs maximum), this spring cannot be overly powerful. When a run-away gun is encountered, the first item to check is the sear spring. Examine the sear spring to be sure it is not broken, or damaged. Additionally, serious problems can arise if the sear spring has taken a set over time. It can progress to the point where the operating rod is able to over-ride the sear nose if it is not being pushed far enough upward. Sear springs are an often-overlooked maintenance item, but should be routinely replaced with a progressive maintenance policy every 3,000 rounds at least. It is also acceptable to replace the stock spring with a custom spring with a higher spring rating. The compression length must remain the same to prevent jamming of the mechanism. Proper trigger manipulation combined with a higher rate custom sear spring will greatly increase the useful life span of sears and operating rods as they will encourage proper, full face surface, engagement of the two parts.

Finally, the recoil spring should be inspected. There are two variants of recoil springs currently available, and each has its own advantages and disadvantages. The gun was originally fitted with a multi-strand spring to combat the well-known tendency for single wire coil springs to potentially lose some of their strength rating due to spring wrap. The use of a multi-strand spring is exceedingly effective in the M60. However, with use it can become damaged as the spring itself is in nearly full contact with the inside surface of the operating rod tube and over time this will cause wear to occur in the form of flat spots There is nothing that can be done to totally prevent this from happening, it is inherent in the design of the recoil system. In order to allow the spring to deliver its greatest possible useful life, the coils should be checked often for flat spots, and the spring wire itself should be rotated to a different indexing each time the gun is disassembled so that wear is spread around the full exterior of the wire rope coils as much as possible. It a flat spot has completely worn through one strand, or is close to doing so, the spring should be replaced. The newest single strand coil spring introduced with the E3/E4 variants is intended to help eliminate the flat spotting associated with the wire-rope type spring. While the new spring design is also quite efficient, the single strand spring also requires the use of its own dedicated guide rod as the coil wire diameter is different than the older version spring. The new style spring can also be prone to wear, and is more susceptible to spring-wrap damages if strained. If this occurs, it can jam inside the operating rod spring tube, and become difficult to disassemble.

Although either version of main recoil spring is serviceable in the civilian realm, the surplus older style wire-rope springs are much less expensive and no new guide rod is needed. For use of either type recoil assembly, the spring guide rod should be smooth and free of any nicks or burrs that may catch a wire strand. Polishing of the spring guide rod to eliminate as much friction as possible is beneficial. Also, liberal use of lubricant inside the operating rod tube, the spring, and along the spring guide rod is recommended to enhance spring life, as long as this excess lubricant is thoroughly cleaned after each shooting session to preclude accumulation of abrasive material.

The recoil buffer unit and its retention yoke must also be inspected. The buffers in use since the mid-1960s and currently still issued are sealed hydraulic spring type, and essentially are maintenance-free except for periodic inspection for damage, including leaks. If the buffer starts to fail, often the first sign will be marked increase in pounding felt at the shoulder stock by the operator, The buffer retainer yoke will also begin to deform in a backward direction. If left unattended, the yoke may cause damages to the receiver channel and guide rails, along with the butt stock eventually. If the rear face of the butt stock appears dented or deformed outward, immediately inspect the buffer assembly and buffer retainer yoke. If any obvious signs of fluid leakage from the buffer body are present, replace the entire buffer unit.

The buttstock itself is supplied as a manufactured assembly, and cannot for all practical purposes, ever be disassembled or repaired beyond minor touchup of the finish. Individual spare parts are simply unavailable for this assembly, unless from a salvaged unit that has been broken down.

This brings us to the last and final area of consideration on the M60, which we will cover in Part 5 next month. It is an area that results in the most common problems and the costliest repairs for the civilian owner, yet virtually all of these problems are avoidable.

Miniature firearms have held the fascination of those interested in weapons for centuries. The art of producing scale models of firearms goes back to the 15th century and continues up to the present day by just a few highly skilled craftsmen. These firing and non-firing examples of high quality craftsmanship are not toys nor were they ever intended to be toys. These beautiful and exact works of art were designed and built to convey the skill of the arms maker and had to be exact in every detail. Cherished in museums all over the world are precise miniature examples of wheel locks, flintlocks, rifles, handguns, shotguns, Gatling guns and machine guns.

The skill of the craftsman is evident as they must use many different manufacturing techniques to produce a miniature that looks and feels “right” and is proportionally correct to its big brother right down to the proper sizing of the grain in wood stocks and fixtures. This was essential as not only were they made especially by commission for the demanding wealthy, but many of these miniatures were actually used as salesman samples by the arms makers themselves.

Manually operated rapid fire weapons are not technically classified as machine guns since the firing mechanism is not self sustaining. Though rapid fire is obtainable, each shot is the direct result of a deliberate physical action by the firer. They were, however, the first to provide a fairly reliable operating principle that afforded a higher volume of fire that was never achieved before especially with the advent of what we now consider to be the modern cartridge. Gatling guns have always held a fascination in the hearts and minds of shooters and collectors. Developed in the early years of the Civil War by Dr. Richard Gatling, his invention could fire at the previously unheard of rate of 200 rounds per minute. It was truly revolutionary. Used by many countries from around the world, his guns saw service from China to the Sahara and in conflicts from the Civil War to the Rough Riders charge up San Juan Hill.

One of the very first to tackle the complex task of creating quality operating miniatures of Gatlings was Dennis Tippmann of the Tippmann Arms Company. Dennis, a true mechanical genius, made a name for himself in the late 1970s by producing in 1/2 scale approximately twenty five Model 1862 Gatling guns in cal. .38 Special. It seems fitting that he chose the Model 1862 as that model was the very first model of a long line of Gatling guns made for almost 50 years with many incarnations and modifications.

In the 1980s, Furr Arms Gatling Gun Company produced a wide array of beautiful working Gatling guns in 3/4, 1/2, 1/3 and 1/6th scale in a variety of calibers. Models produced included the 1874 Gatling, 1876 Camel Gun, 1883 Gatling and 1893 Police Gun. A family business, Furr Arms always had the greatest emphasis on attention to detail in every aspect of their manufacturing process. Castings were designed in miniature from original Gatling parts and cast in their own foundry. After many hundreds of hours of work on each gun, the result is a working miniature that is so graceful and beautiful that one can hardly believe their eyes.

The legacy of making operating Gatling guns in multiple scales in the 1990s has been taken up by master machinist Richard Pugsley of Thunder Valley Gatling Gun Company in Palmyra, Nebraska. His Gatlings range from full scale in .45-70 govt. to 3/4 scale in 9mm and he is working on a 1/3 scale in .22 caliber. His guns are always a crowd pleaser at the semi-annual Knob Creek shoot. His quality and attention to detail carries on a culture of arms making that goes back many centuries. But even his Gatling manufacturing future is in doubt thanks to the Gun Control Act of 1994 which prohibits the manufacture of magazines, clips and feeding devices of over 10 rounds. He still has some guns in inventory with the full magazine capacity but when they are sold he is about done. Would you want to then buy a ten barrel Gatling gun for ten or twelve thousand dollars with a ten round magazine? And for you do-it-yourself types, there are ads for operating Gatling gun plans for sale but be warned. You can build the gun but if you build a magazine for it of more than ten rounds you may very well be looking at doing hard time in the Big House.

The Hotchkiss Revolving Cannon was invented by Benjamin Hotchkiss, an American, who went to France in 1867. He originated the 37mm projectile with a bursting charge and his revolving cannon was specifically designed for flank defense. Unique to it was that each barrel was rifled with a different pitch allowing the target to be “swept” by shrapnel. Though resembling a Gatling gun in its outward appearance, it is an original design. It has a single firing pin and a single loading piston and the barrels rotate intermittently thus allowing a pause during rotation at the moment of firing. This innovation eliminated the centrifugal force affecting the bullet when firing such guns as the Gatling where the whole mechanism revolves continuously at a high rate of speed during firing. The 1/4 scale Hotchkiss Revolving Cannon as built by Mike Suchka is a faithful operating rendition of the original.

Also commonly confused with the Gatling gun is the Gardner gun invented by William Gardner of Toledo, Ohio in 1874. It can be readily identified by the square receiver and horizontal alignment of the barrels with a bolt behind each barrel. The reciprocating bolts fired each barrel alternately left, right, left right, etc. in the two barrel model. There was a later version that had five barrels that operated in sequence. It was an extremely reliable weapon but the U.S. already had their Gatlings and dismissed it. Though the British used Gatlings very successfully, it was the British Royal Navy and then the British Army that ultimately embraced the light weight and dependable Gardner gun and it was deployed around the world to the far corners of the British Empire. It proved itself in battles in the Sudan at El Teb, Tamasi and the Upper Nile in the mid 1880s and in multiple skirmishes wherever the Empire needed to exert itself.

Of course any firearm can be the subject of a miniature rendition but it is the skill of the machinist that dictates the care and quality in which it is made. In a tradition dating back almost 500 years, it is still carried on today by a small group of craftsmen who do it for the love of the craft.

In this, the third part of the HK ID guide, we are covering the basic semi-automatic variants imported into the United States by HK in Sterling Virginia. In later parts to this series, SAR will cover the clone imports and other manufactured variations of the HK line. SAR would like to thank Jim Schatz of HK Federal Operations for his assistance in this part of the series, and his and HK’s help in general. As an aside, the SL8-1, a semi-automatic version of the G36 rifle with a special ten round magazine has just been approved for importation. We were unable to obtain photos before presstime, but SAR will be doing an in-depth report on this.

SP89

BBl length 4.5″ O/A length 13″ Weight 4.4 Lbs mag capacity 15 or 30 rounds. Utilizes the HK recoil operated, delayed roller locked bolt system.

The SP89 is a 9mm semi-automatic pistol that is frequently used with a registered HK conversion sear to create an MP5K clone

HK 94

Cal: 9mm x 19 weight: 6.43lbs OA length: 34.59″ Bbl length: 16.54″

The two basic buttstocks on the HK semi autos are the fixed stock (A2) (Shown) and retractable stock. HK94 markings are on the top of the receiver, to the front of the sight. The HK94 is a true semi-automatic in that it uses a clip on trigger group. Probably the most desirable of the HK semi’s, the HK 94 has been the host gun for many registered sear and registered receiver conversions to the MP5 format (Not by HK, of course). It is the host gun for the clone MP5’s, MP5SD’s, and pre-SP89 MP5K’s.

HK 93

Cal: .223 weight: 7.75lbs OA length: 35.5″ Bbl length: 16.13″

The HK93 is the semi-automatic version of the HK33 rifle. This was used as the host rifle for registered HK sear conversions to HK33, HK53, and 53k variants in the US.

HK 770

Cal: .243 or .308 weight: 7.5lbs OA length: 42.8″ Bbl length: 19.6″

Manufactured in .243 and .308, this hunting rifle used the HK delayed roller locked bolt system and polygonal rifling. Registered HK sears are not usable in this series.

HK SL7

Cal: .308 weight: 8.37lbs OA length: 39.96″ BBl length: 17.71″

The SL7 is the German Army Reserve training rifle. The sights approximate those of the G3 rifle. It has a unique carbine stock and shorter barrel than the HK770.

HK 91

Cal: 7.62x51mm weight: 9.5lbs OA length: 40 1/4″ Bbl length: 19″

The HK91 was the flagship of HK rifles- it is the semi-automatic version of the famous G3 rifle. Registered HK sear installations were done to many of these, and it is the host rifle for G3, HK51, and HK 21 conversions in the US.

HK 911

Cal: 7.62x51mm weight: 10.9lbs OA length: 42.5 ” Bbl length: 19.7″

This is the original “Thumbhole stock” version of the HK91 rifle. These were HK91’s that had the barrel sleeved to get rid of the frightening threads, and a new stock and forend added to bring them into compliance with the 1989 ban on importation of scary “Assault” rifles. The “1” was stamped on to make it “911”.

HK SR9

Cal: 7.62x51mm weight: 10.9 lbs OA length: 42.5″ Bbl length: 19.7″

The SR9 is the final version of the HK91 “Import friendly” rifle that was imported from 1989 to 1994.

MSG90

Cal: 7.62 x 51mm OA Length: 45.87″ BBl length: 23.62″ weight: 14.11 lbs.

The MSG90 Sniper Rifle is one of the finest semi-automatics in the world, but it uses a swing down lower and is considered a machine gun. Standard accessories include the 10x Hensoldt scope, Stanag mount, and a crisp 3 lb trigger pull with adj. Shoe.

MSG90A1

The barrel is threaded to accept a flash hider or suppressor. In addition, the A1 has a hooded front night sight and 1200 meter adjustable rear sight. A brass deflector is standard on the A1, just to the rear of the ejection port.The MSG90A1 was originally referred to as the MSG90-DMR (Designated Marksman Rifle).

PSG1

Cal: 7.62x51mm weight: 17.86lbs OA length: 47 5/6″ Bbl length: 25.59″

The PSG1 Sniper Rifle is a highly refined version of the HK91 rifle. It uses a clip on lower so is a true semi-auto in the US.

SR9T

Cal: 7.62x51mm weight: 10.6 lbs OA length: 42.5″ Bbl length: 19.7″

The “import friendly” SR9T is the target version of the SR9 rifle. It utilizes the PSG1 trigger group and the MSG90 buttstock.

SR9T-C

Cal: 7.62x51mm weight: 10.9lbs OA length: 42.5″ Bbl length: 19.7″

The “import friendly” SR9T-C was the Target / Competitor version of the SR9 rifle. It utilizes the PSG1 trigger group and buttstock.

Having designed, series produced, and deployed its MGP-79/MGP-79A/MGP-87 series of 9 x 19 mm caliber submachine guns, Peruvian Navy’s SIMA-CEFAR organization had by the mid-1980s accumulated considerable experience and was ready to launch a more ambitious program. Those weapons, although possessing the due credit of having launched the country’s first-ever indigenous small arms manufacturing program, generally represented what is commonly termed as “second-generation” SMGS. Weapons like the WWII-vintage German MP38, British STEN, the American M3 Grease Gun, and many others that appeared worldwide after the War. Except for one or another refinement, Peru’s MGPs basically incorporated the same characteristics. Size and weight were two of them.

Even with the stock folded, the MGP-87, for example, was 500 mm long, and, minus magazine, its weight just about touched the 3-kg mark. When one opts or a submachine gun, he or she is clearly trading cartridge power and range for lightness and compactness. The search for “firepower in a compact package” has for long existed. In the 193os, the Royal, Astra, and Mauser “Schnellfeuer” machine pistols were unsuccessful attempts to achieve this goal. The American Ingram M10/M11 series was somewhat more (although not entirely) successful, and some other subguns (Israel’s Mini and Micro Uzis, and Germany’s H&K MP5K, for instance) later appeared to fill this highly specialized niche. Not to mention more recent, radical designs such as Britain’s Bushman IDW (Individual Defence Weapon) and Austria’s Steyr TMP (Tactical machine Pistol).

Local operational requirements and potential export market possibilities formed the basis for the development of the MGP-84 (at one time designated MGP-15), which has been in production at the Callao naval Base, near the capital city of Lima, for several years. Besides adoption by Peruvian forces, it has reportedly been exported to such countries as Argentina, Honduras, and Mexico.

Compactness was, obviously, a primary design objective. This has been remarkably well achieved in the MGP-84, whose telescopic (or wrap-around) bolt entirely surrounds the 166 mm-long barrel, pretty much in the same fashion of a Colt Government Model pistol, for example. The return spring is positioned in a similar way, too, encircling the barrel. Many people don’t favor placing any spring too close to a heat source (a hot barrel, in this case), as this may lead to losing its temper, and it still remains to be seen whether, in the long run, this problem is going to manifest in the Peruvian gun.

Following a current trend in small arms manufacture, synthetic material is used in the construction of the main body (pistol grip/magazine housing, trigger guard, and firing mechanism housing), to which the steel tubular receiver is attached by two removable pins. The buttstock consists of a steel arm and a synthetic buttplate, and neatly folds to the right side of the gun, thus reducing overall length from 503 to only 284 mm, a mere 67 mm longer than a Beretta Model 92 semi-auto pistol, for example. This easily allows the Mini to be carried concealed under a coat or jacket (the manufacturer offers a dedicated shoulder holster for that) and quickly brought into action. This should prove most useful for bodyguard duties.

I have been invited by SIMA-CEFAR to test fire the MGP-84 at one of the Peruvian Navy ranges at Callao. Since that intense training activity by Navy (“Marina de Guerra”) and Marine (“Infanteria de Marina”) combat teams was taking place everywhere at the time of my somewhat unscheduled visit, I could not count on a formal shooting range (paper targets, etc) for my use. Instead, I had at my disposition a reasonable free area, surrounded by sand dunes, with a usable range of roughly 50 meters, which comes to be a realistic firing distance as far as small submachine guns are concerned. Informal (empty soda bottles and wooden crates) targets happened to be spread over the place at every imaginable distance. Ammunition supply was plenty, consisting of locally made FAME and Brazilian CBC/Magtech 9 x 19 FMJ rounds.

Like the previous MGP-79 and MGP-87, the “84” employs 20- and 32-round magazines similar to and interchangeable with those of the Uzi family, which, for the record, finds wide acceptance by Peruvian armed and police forces. This type of box magazine is of the staggered-row, two-position feed type, which is easier to load by hand and requires reduced bolt effort to strip rounds and feed them into the chamber. Not at all surprisingly, the magazine catch button occupies the same (low, left side) position in the pistol grip and is a carbon copy of the Israeli guns, but nothing else relates the two designs.

Controls are adequately sized and located. The fire selector, situated just above the forward end of the unusually wide, very sturdy trigger guard, has the settings “S” (safety), forward; “1×1” (semi-auto), top; and “A” (automatic), to the rear. Its manipulation is done with the thumb of the left (supporting) hand, easily, quickly, and effortlessly. It has been a frequent practice in many guns to place the selector switch closer to the main grip so that it can be, tentative and optimistically, actuated with the thumb of the right (firing) hand, but in quite a few instances its shape and/or actual positioning prevents this from happening. So, the MGP-84 Mini solution is straightforward.

The cocking knob, at about 45 degrees to the left, is attached directly to, and reciprocates with the bolt. Its size is large enough to allow positive manipulation, and small enough to avoid snagging in clothes, pieces of individual gear, bushes, etc.

With the stock extended, the gun provides adequate comfort for accurate, aimed fire, mainly when one chooses the semi-automatic mode. The protected sights (U-notch, flip-type rear sight, and post front sight) are easy to acquire and adjustable for 100 meters (in my view, the maximum realistic engagement distance for such a short barrel)) and 200 meters (a most optimistic proposition). Anyway, my available range did not go past the 50-or-so-meter mark and the weapon proved entirely capable of consistently hitting man-sized targets. At shorter distances (say 10 to 15 meters), head shots may be a viable choice to deal with emergency tactical situations, such as in a hostage rescue mission.

Since the beginning, I was particularly anxious to try the Mini in the automatic mode, and I’ll tell you why. Similarly-sized SMGs (Ingrams, Mini and Micro Uzis, MP5Ks, etc.) have inherently a high cyclic rate of fire, usually in the region of 1000 to 1200 rounds per minute, which does nothing to help in controllability and, consequently, in practical accuracy … past arm’s length. Since SIMA-CEFAR literature mentioned 650-700 rounds per minute for the MGP-84, I was more than eager to try it.

Although the shooting was not instrument-monitored, my accumulated experience with buzzguns made me believe that the quoted figures are pretty real. Even during normally useless very long bursts, controllability remained excellent, both firing from the shoulder and from the waist level. Using trigger control alone, short, two-round bursts and single shots are simple to master after some familiarization.

If required, the Mini can be fired with the buttstock folded. You can do it single-handed, like a pistol, or even using the folded buttplate as a forward vertical grip. Be aware, however, that no matter what Hollywood suggests, this is a sure way to lose a lot in terms of accuracy: just do it in case of a real emergency … and at very close ranges!

The Peruvian submachine gun’s compact size makes it an ideal weapon for covert, low profile missions. Much more so if you fit it with a sound suppressor. In just a few seconds, unscrew the forward receiver cap and substitute it for the locally designed silencer unit, which, thus, attaches to the original barrel. It is relatively light, not too bulky, and, boy, does it work! Without requiring the use of subsonic ammunition, it effectively cuts down the firing signature to slightly more than the metallic noise of the reciprocating bolt. The added weight, in fact, increases firing stability, and were the MGP-84 one of my tools-of-trade, I’d probably have it with the suppressor on most of the time for serious business.

SIMA-CEFAR (renamed SIMA Electronica in 1996) also offers a semi-auto-only version of the gun, a sort of ultra-compact carbine designated MGP-84C (at one time, MGP-14), for those not requiring – or not allowed to have – an automatic weapon. Those creative Peruvians built and tested a stockless, assault pistol variant, the MGP-14 Micro, in 1994, but the project did not go beyond the prototype stage.

TECHNICAL SPECIFICATIONS MGP-84 Mini

Cartridge: 9 x 19 mm
Operation: Blowback, selective fire
Feed: 20- or 32-rd detachable box mag.
Weight: no magazine: 2.3 kg, full 32-rd magazine: 2.9 kg
Length: stock extended: 284 mm, stock folded: 284 mm
Barrel length: 166 mm
Cyclic rate of fire: 650-700 rounds/min.