By Paul Newhouse

Since the start of Operation Iraqi Freedom, most everyone have heard or seen news reports about the employment of RPGs by anti-Coalition forces; or what are referred to as “Rocket Propelled Grenades” by the news media. While the weapon shown is almost invariably the RPG-7, with perhaps an odd RPG-2 thrown in, there’s a lot more to the RPG story than those one or two familiar systems.

Perhaps we should start with a bit of etymology. While “RPG” has had three different meanings in the past 65 years, the acronym has never stood for “rocket propelled grenade.” Indeed, all the early RPGs had no rockets of any kind incorporated into their design, and the ubiquitous RPG-7 fires grenades both with and without rocket assist.

The first RPGs were simply shaped charge hand grenades. “RPG” in their case stood for Ruchnaya Protivotankovaya Granata – Hand Antitank Grenade. (The author wishes to apologize in advance for any improper transliterations of Russian, though his spellings are more or less phonetically correct.) The two best known examples were the RPG-43 and RPG-6. While resembling stick grenades or “potato mashers” with large heads, their method of operation was rather more complex. Upon pulling a safety pin and throwing, a safety lever on the handle separated, allowing a stabilizing drogue chute to deploy, ensuring that the grenade impacted top down. A later version produced by the Russians was designated RKG-3, with the “K” standing for Kumulativnaya – shaped charge – to preclude confusion with the later kinds of RPGs. This design was copied by Yugoslavia as the M79. These grenades remain effective against all but the most modern armored vehicles. In fact, the US Army in the 1980s reverse-engineered an East German design. Their fatal flaw is their short effective range, approximately 30 meters.

The first of the weapon systems to resemble today’s RPGs was the RPG-1, development of which started at the end of World War 2. In this case, “RPG” stands for Ruchnoi Protivotankoviyi Granatomyot – Hand Antitank Grenade Launcher. Despite Russian protestations that it was developed independently, the RPG-1 clearly owes much to both the German Panzerschreck rocket launcher (for the design of the warhead) and the Panzerfaust recoilless launcher; particularly the late-war reusable versions. The RPG-1 utilized the Panzerfaust’s simple launch tube, and as a result had to employ a black powder propelling charge that produced a very low muzzle velocity. The RPG-1 was not produced in large numbers.

The first widely produced RPG was the RPG-2, introduced in the late 1940s or early 1950s, coincidentally at the same time the AK-47 was beginning to enter service. This again utilized the Panzerfaust-type straight tube recoilless launch system, but now the PG-2 (Protivotankovaya Granata – Antitank Grenade) grenade bore a very obvious resemblance to that of the Panzerfaust 150, with a conical nose, cylindrical mid-body, and tail boom with wraparound fins. As the RPG-2 was thoroughly described in a previous issue of SAR (Vol. 10, No. 3), no further description is offered here.

Both the RPG-1 and RPG-2 were tactically comparable to the US “Bazooka” and British PIAT, being different systems capable of operation by a single man, but normally served by a two man crew. At about the same time as the RPG-2 was introduced, a heavier anti-armor weapon system also came into service. This was the 82mm SPG-82 (“SPG” stood for Stankovoi Protivotankoviyi Granatomyot – Mounted Antitank Grenade Launcher), development of which also began late in World War 2. Unlike the RPG-1 or RPG-2, this was a rocket system comparable to the US M20 3.5in “Super Bazooka.” Despite the smaller caliber, the SPG-82 was heavier and longer than the M20, with a large shield with wheels provided for the two man crew. The SPG-82 may be considered almost a general purpose infantry support weapon, akin to the early US recoilless rifles, as it had both PG-82 antitank grenades and OG-82 (Oskolochnaya Granata) fragmentation grenades. Both of these “grenades” were of course rockets.

At this point it may be wise to digress a moment and differentiate between infantry antitank weapon systems that are rockets, and those that are recoilless guns. Most frequently the majority of such weapons are described as rocket launchers, but this is glaringly inaccurate. The well-known M136/AT4 single-shot weapon in widespread use by the US Army is in fact a disposable recoilless launcher. The infamous RPG-7, despite firing rocket-assisted projectiles, is a reusable recoilless launcher.

One supposes the key distinguishing feature is where the pressure, built up by propellant combustion, occurs, and where the pressure drop which produces the propulsive force occurs. In a rocket system, the propellant combusts entirely within the rocket itself, and the pressure drop which produces the propulsive force occurs across the body of the munition. This may best be illustrated by considering the case of a rocket like that from an M72 LAW being ignited outside its launch tube. The rocket would travel just as far as if it were fired normally; the tube only provides for initial aiming, and does not contribute to the propulsive process.

In a recoilless weapon, the launch tube is an integral part of the propulsive process, and incorporates a chamber for the propellant to burn at a relatively high pressure, and a nozzle to create a constriction that vents the high pressure gases rearwards, usually at an accelerated velocity, whose momentum is then used to balance exactly the momentum of the projectile leaving the muzzle. If one were to ignite the propelling charge of a PG-2 or a PG-7 in the open, it would simply burn. The grenade would not go anywhere. Without a chamber to allow burning at a high pressure, no propulsive force is generated.

It’s also worthwhile to take a brief look at the physics of recoilless weapons. Simply put, recoilless guns work by expelling a projectile from the front in the usual manner, and a countermass out the back of the gun. The earliest recoilless guns were the Davis Guns of WW1. These used a central propelling charge to fire a projectile out of a forward-pointing barrel, and a solid countermass of equal weight out a rearward pointing barrel of identical length. While solid countermass recoilless guns have been in use since then, and a few still are, in most applications a solid countermass is a nuisance at best and a danger to one’s own troops at worst. Between the wars it was found that it was only necessary to match the momentum (mass times velocity) of the countermass to that of the projectile. Thus, a very light countermass, such as propellant gas moving at a very high velocity, can have a momentum equal to a heavy projectile discharged at a lower velocity.

Most recoilless guns using a propellant gas countermass feature a prominent nozzle or nozzles at the back of the weapon. These are sometimes called venturis (acceptable) or “blast cones” (incorrect); more on these below. But one can’t help but note that the Panzerfausts and the RPG-2 had simple straight-tube launchers with neither constricting orifices nor conical venturis. So how did these weapons function, without simply venting the propellant gases out the back at low pressure? The answer lies in the fluid mechanics of compressible fluids. Most of us are aware that passing a fluid through a constriction will raise the velocity of the fluid. (Simply take your garden hose and constrict the water stream with your thumb, and watch how the water speeds up.) The higher the upstream pressure the greater the downstream velocity. But in gas systems, this only happens until a condition called choked flow is reached. At that point further increases in upstream pressure do not cause further increases in downstream velocity. The result in a recoilless weapon is a rise in pressure sufficient to launch a projectile. While this principle is the basis for most recoilless weapons, in straight tube launchers it has substantial performance limitations.

The outlet velocity of the propellant gases in a straight tube launcher remains subsonic. And to achieve a choked flow situation quickly, very fast burning propellant is required; in the RPG-2 fine granular black powder is used. But this fast propellant in turn causes a rapid pressure rise in the area of the propelling charge. The maximum pressure must be limited to remain within the strength limits of the tube. So there’s a limit to the weight of propellant that can be used, which in turn limits the mass of propellant gas available to form a countermass. As already mentioned, the gas velocity is limited in this system as well, the result is a relatively low available counterrecoil momentum. The final result of all these limiting factors is a very low muzzle velocity for a projectile of useful size. This was readily apparent in the early Panzerfausts, whose effective range was severely limited, at first to only 30 meters, by their low velocity and resultant highly curved trajectory.

Since gas velocity and tube strength impose limits on available counterrecoil momentum, the only way to really improve this system’s performance was to add additional propellant (and thus additional gas for the countermass), and since increasing the charge attached to the projectile would only increase the local pressure to unacceptable levels, the only solution available was to apply the maximum operating pressure over a greater length of the launch tube by distributing the propelling charge. In the later, longer-range Panzerfausts this was achieved by adding a secondary propelling charge approximately in the middle of the launch tube. The charge at the base of the projectile was initiated in the usual way, and this in turn ignited the secondary charge, boosting muzzle velocity and thus range, up to 100 meters and more.

The RPG-2 uses a rather more ingenious solution, with the black powder propelling charge subdivided into 6 increments by means of cardboard tubes and discs, the latter with flash holes to foster ignition. The primer in the base of the PG-2 grenade ignited the first increment, which burns rapidly, creating pressure and pushing the remaining four increments back down the tube. After a few inches of travel, the second increment is fully ignited, then the third, fourth, fifth, and sixth. The result is high pressure over a greater length of the tube, rather than merely at the base of the projectile, and a greater volume of propellant gases for both propulsion and countermass.

But even with this technique, there were limits to the performance of a simple straight tube launcher. One attempt at improvement was the Yugoslav M57 launcher, which incorporated a partial solid countermass in the form of a quantity of sand. However, this represented at best an incremental improvement over the simple straight tube launchers.

But back to the RPG story! While the PG-2 grenade performed well enough in terms of armor penetration (and remains a threat to all but the most modern armored fighting vehicles), the weapon’s fatal flaw was its very primitive recoilless launcher. While its simple cylindrical tube was easy and cheap to fabricate, its lack of a chamber and nozzle, and resultant low pressure combustion, as described above, severely limited the velocity of the PG-2. This made range estimation very important at all but the shortest ranges. Additionally, the low velocity meant a longer time of flight. Both factors limited hit probability against both stationary and moving targets. An interim solution was found in the RPG-4. While this fired purely ballistic grenades, which resembled PG-2s albeit with increased standoff for the shaped charge, the 45mm diameter launch tube incorporated a larger diameter chamber and a venturi, or nozzle, at its rear end, causing it to greatly resemble its successor the RPG-7. The RPG-4, developed in the late 1950s, was not produced in quantity.

A brief description of the physics of the RPG-4 and RPG-7 is in order. These weapons incorporate the features seen in other, larger recoilless systems: a chamber of larger size than the propelling charge, and a convergent-divergent nozzle incorporating a constriction and a divergent (outlet diameter larger than inlet diameter) conical section. The constriction sets up the choked flow condition described above, albeit without the need to use a very fast propellant. The conical divergent nozzle in turn accelerates the propellant gases to supersonic speeds. Thus, in this type of system, there is much more counterrecoil momentum produced, both from burning more propellant over a longer time and from expelling the gas countermass at a much higher velocity. In the case of the RPG-7, this allowed the launching of projectiles heavier than PG-2s at velocities in some cases approaching double those of the older system.

The RPG-7 recoilless launcher, introduced in 1961, reverted to the 40mm tube diameter of the RPG-2 while retaining the chamber and nozzle design of its precursor the RPG-4. As the RPG-7 and its ammunition have already received a thorough treatment in the pages of SAR (Vol. 10, No. 3), no further description of the system will be given here. A brief observation on the function of its ammunition will be made in the hope of finally putting to rest the absurd “rocket propelled grenade” name. The RPG-7’s principal munition is one of a series of PG-7 antitank grenades. All of these incorporate a rocket motor. As the RPG-7 is a recoilless launcher, the PG-7 may be considered a rocket-assisted projectile; calling it a rocket would be incorrect. The reason for adoption of a recoilless-launched, rocket-assisted antitank munition of greater-than-average complexity is simple: it increases the munition’s velocity and thus reduces its trajectory and time of flight, without imposing any additional penalties on either the launcher or its user. The result is greatly improved hit probability against both moving and stationary targets. In a 1970s study the US Army deemed the RPG-7 the best solution to hitting armored vehicles out to 300m. Better than pure rocket systems and better than pure recoilless systems. But what would happen if the rocket motor in a typical PG-7 failed to ignite 10-15 meters from the launcher like it’s supposed to? All that would happen is that the grenade would follow a purely ballistic trajectory to the target, take longer to get there, and impact below the desired aimpoint. The shaped charge in its warhead would function just as well as if the rocket motor had fired, since the VP-7 fuze is independent of the rocket motor.

Another heavier system was introduced just after the RPG-7, the 73mm SPG-9 smoothbore recoilless gun. Though it filled a similar tactical role as the earlier 82mm B-10 and 107mm B-11 recoilless guns, it is a significantly lighter and handier weapon, which may explain its “SPG” nomenclature. Like the SPG-82, the SPG-9 fires two natures of ammunition: the PG-9 antitank grenade (which is rocket assisted for the same reasons the PG-7 is), and the OG-9 fragmentation grenade (which is an unassisted, purely ballistic munition).

A less-well-known weapon system, whose intended employment is also not as well known, is the RPG-16. Although its nomenclature may lead one to believe it was a replacement for the RPG-7, it really isn’t. The RPG-16 has a bore size of 58mm, and as it does not use an overcaliber warhead, its antiarmor performance is significantly less than more modern versions of the PG-7. At the same time the RPG-16 is significantly heavier than the RPG-7. So rather than looking at the RPG-16 as a successor to the RPG-7, it may be more appropriate to consider it as a subcompact derivative of the SPG-9, for use in those situations where the larger and heavier SPG-9 may be unsuitable. One Russian source mentions that the RPG-16 was developed primarily for airborne troops; its two piece takedown design, similar to that of the RPG-7D, seems to bear this out.

The third meaning of “RPG” is Reaktivnaya Protivotankovaya Granata, applied to a number of disposable pure rocket systems similar to, and likely inspired by, the US M72 LAW. “Reaktivnaya” is awkward to translate; some sources say jet, others rocket, and others “propulsive.” (Perhaps the best way to think of it is as “reactive propulsion,” in other words, a rocket). Also note that the whole system together is not a Granatomyot (grenade launcher), but a Granata (grenade).

The earliest such Russian system was the 64mm RPG-15, which was produced in only limited numbers. This was followed by the very widely produced 64mm RPG-18, also previously covered in the pages of SAR. The RPG-18 was augmented, but not really supplanted, by the 72.5mm RPG-22. Both of these systems employ rocket motors and folding fins inspired by the M72 coupled to warheads essentially identical to those used in PG-7s.

There are newer RPGs which have been designed and produced by the Russians: the RPG-26, 27, 28, and 29. The first three are single-shot weapons, while the last is a long and somewhat unwieldy reusable launcher. All feature larger diameters for improved armor penetration, and some feature tandem warheads for improved effectiveness against reactive armor. But as these systems have not been produced or fielded in large numbers, they will not be considered further.

Finally, there are two additional systems called “RPGs,” produced in Warsaw Pact countries, which have nothing in common with any of the RPGs previously mentioned, but which are so novel that they must be mentioned, if only in passing. While the grenade of the single-shot Polish RPG-76 Komar (Mosquito) resembles a small PG-7, in fact the RPG-76 is a pure rocket system; the rocket motor ignites upon firing, and its PG-7-like nozzles direct the exhaust gases away from the firer. Even so, it must be quite disconcerting to fire this weapon. The launcher is simplicity itself, consisting of a short tube with a folding shoulder stock and crude sights and trigger mechanism.

The single-shot Czech RPG-75 is as finely finished as the Polish weapon is crude. While its light launch tube may lead one to believe that it’s a rocket system, in fact it’s a smoothbore recoilless high-low pressure launcher, the only such weapon ever fielded, successfully combining the two novel gun propulsion technologies pioneered by the Germans and others in WW2. Because the RPG-75 has a separate high pressure chamber, the launch tube does not need to be as heavy as in a conventional recoilless launcher. Finally, the RPG-75’s projectile is neither fin nor spin stabilized, but uses a rear spoiler for stabilization. The only other application of this stabilization technique the author is aware of is in the 120mm M831A1 practice cartridge fired by the M1A1/A2 Abrams tank.

Now that you know the history of the RPG family of weapons and munitions, try not to cringe as the author does upon hearing or seeing the term “rocket propelled grenade!”

Dear readers of Raffica: On occasion a subject question becomes too large for our normal Q&A format. When that occurs, we move to a “Raffica Special” and we are in that position right now. We have had so many questions regarding the operation of the RPG-7 system that the only way to properly answer this is with a “Special.” Since I have been working on a photo ID series of the various basic RPG systems for many years, and we were just preparing to do the ultimate worldwide ID Guide to these launchers, we decided to prep the readers with this How It Works guide first. Several other articles will soon follow including the RPG ID Guide and an in-depth analysis of the sighting systems. We hope this guide helps dispel many of the myths surrounding the RPG-7 system, and educates our readers to the basic functions and differences. – Dan

Shoulder fired rocket launchers are nothing new. Neither are rifles with integral grenade launchers for that matter. In the 18th century, there were seven foot long flintlock style rifles that a rocket shaft was aligned in, and a transfer bar operated the flintlock mechanism located out at the front of the launcher. The buttstock, trigger group, etc., look normal, then the lock was out at the very front. There was another design from the same period where the buttstock was cylindrical and opened up at the shoulder end to make a cup style grenade launcher. The lock was able to fire either the musket barrel or the grenade launcher with the flick of a switch. The grenade launcher was used mortar style of course. These are mentioned simply to show that weapons designers have been making man portable launchers and hurlers for centuries. It is only in the modern times that we have fine tuned the process.

The roots of the RPG-7 launcher can be found in the German Panzerfaust (literally “Tank-Fist” in German) of World War II. This was little more than a tube with a firing mechanism to launch a primitive warhead, but it gave the infantryman the ability to launch an explosive charge farther than he had been able to previously. Developments during and after World War II went in several directions, with some countries concentrating on the recoilless rifle principle and others looking more to shoulder fired rocket launchers.

In 1948-49, the Soviets introduced the RPG-2 system. The RPG-2 initially was a simple tube with a rocket propelled grenade that was fired from it. Behind the rocket was an expeller charge that basically threw the rocket forward from the tube, and then a pyrotechnic fuze fired the rocket itself when it was safely in front of the operator. The RPG-2 rockets were not reliably timed for firing so the accuracy degraded at distances beyond 100 meters. Stabilization came from six thin sheet metal fins at the rear of the rocket motor, which did a reasonable job for accuracy. The RPG-2 series had an expected range of 150 meters, so the sights were fixed ladder types with no allowance for adjustment. Later models had some modifications, such as a rudimentary blast shield at the rear to help keep any backblast away from the operator. This was neither a blast cone nor a venturi.

The RPG-2 system was manufactured until its replacement, the RPG-7, appeared in 1962. The Communist Chinese built and distributed the B-40, an RPG-2 variant, and the Yugoslav’s built a much heavier similar launcher called the M57.

It is strongly recommended against firing RPG-2, M57, or B-40 rounds as there has not been recent manufacture and the chemical compositions and fuzes are now untrustworthy. Unless the operator can verify recent manufacture, these should be avoided. The launchers themselves are simple mechanical devices so with fresh ammunition they would be fieldable. Antique, outdated and outclassed, but fieldable RPG-2 series grenades do not have timed safety self destruct fuzes, so a “dud” round will become a UXO (Un-Exploded Ordnance) hazard.

RPG-7

For the purposes of this article, we will be discussing the Russian/Soviet made RPG-7 series: the RPG-7V and RPG-7D. There are approximately 29 different variations made around the world and SAR will be covering models and countries of manufacture at a later date in the ID Guide. Two of the most basic designs have been copied by many countries: the Soviet style and the Chinese style. The fastest way to tell which school the RPG came from is that the Chinese style utilizes a bipod, a shoulder rest, and has adjustable front and rear sights, while the original Russian model does not.

Several initial changes appear in the RPG-7 series. The example in these photos is the second variation, the RPG-7V. The “V” model is simply a bit smaller dimensionally, and lighter. The tube inner diameter remains at 40mm. Several manufacturing method improvements were instituted.

RPG-7D

The RPG-7D is the paratrooper’s takedown version of the RPG-7 system, which appeared in the early 1970s. There is a three lug turning takedown point with various safety features built in to avoid firing without the rear of the tube properly attached. There are two bayonet lugs used to attach the rear section to the forward tube, making for a much smaller package for jumping with.

RPG-18
(Side block of four pics)

Aiming and Boresighting

The objective is to hit the target, and more specifically, to strike a crippling blow to the target. If the target is a tank or self-propelled gun, the goal is to take the gun out of action. Simply taking a tread or other immobilizing shot is good but keep in mind that the operators of the vehicle will be looking to return fire, and even if they are immobilized, if they can bring the main gun to bear then the RPG team is in danger as it takes 8-12 seconds to load another round.

Since the objective is to hit the target accurately, there must be a method of ensuring the sights and scope are in line with the bore. In both cases, this is accomplished by using a bore sight and a point of aim that is a minimum of 900 meters away. At the shop it is easy enough to have a set of blocks and a mount in order to immobilize the tube for this procedure, but field expedient tricks include sandbags and either a table or other flat surface. Remember to leave room with the bags for line of sight on checking the sights. This should be done by unit armorers and the operators as well, just like checking any other weapon sight when getting ready to fire. Well trained teams will constantly check their bore sight.

The bore sight is usually composed of two pieces. They are both tubes and the front has a wire crosshair on it and this is inserted into the front of the tube. Some of these front pieces require the operator to put two strings on it to make the crosshairs making it possible to improvise this front section by crossing two strings over the front of the tube at 90 degrees to each other and securing them in place. As long as the crosshairs are centered, this is fine. The rear tube, if used, has either four slots with an open center, or simply an open center, that slides into the blast cone. Visually check from the rear aperture to the crosshairs in the front of the tube, and this will give you a bore center. It is quite possible to bore sight without the rear section, by moving back a bit further from the rear of the tube when sighting.

With the tube immobilized, the operator should fix the bore sight onto an object at 900+ meters. The object should have some distinct horizontal and vertical features. Once this is sighted, the mechanical sights can be checked. Russian style sights do not have much adjustment to them, but the Chinese family has full windage and elevation adjustment available. Bring the sights in line with the bore sight and the sights are aligned with the tube at all ranges. The scope itself has a single crosshair up above the sighting chart, distinct and by itself. This crosshair is to match the bore sight at 900 meters. Right and left windage and up or down adjustment are controlled by two dial knobs at the front of the sight. Full adjustment will be described in a later article.

The Controversial Optical Sight

Optical sights are controversial because there are several schools of thought on this unit, and it does in fact take a lot of training and live fire practice to use the RPG-7 let alone the optical sight. SAR will be covering the sighting in depth at a later date. Suffice it to say that using this unit requires extensive training.

Advice is frequently given that an operator should immediately throw away the optical sight because it is too complicated for combat conditions. This is good advice if the operator is not going to receive a lot of the proper training; novices should stick to the iron sights. However, most RPG-7 operators are dedicated to this job and do receive a lot of training. If that is the case, the optical sight gives many advantages. Combined with a modern laser range finder, the optical sight can truly extend the range of the RPG-7 from its “point-blank” designated 300 meters to a full 500 meters, depending on wind conditions.

Again, experience with live fire is critical to the RPG-7 operator’s accuracy. In the US, it is difficult to get this experience due to our importation laws on explosives and the fact that the US military has a very wise policy of not allowing the firing of captured ammunition of this type. (In the event that there are US end users reading this who need to arrange live fire training outside the US, please see me after class. – Dan)

The Wind Thing

RPG-7 Rounds

There are many, many rounds on the market today. SAR will cover these at another time. For our purposes, we are going to take a look at the basic HEAT (High Explosive Anti-Tank) round: the PG7B.

1) At the joint between the expeller charge and the rocket booster that is permanently part of the grenade, is the section that initiates the firing sequence. When the firing pin strikes the primer (located in the small threaded hole on the center side in this photo, but primer is missing) the primer ignites a train of events. Immediately the expeller charge to the left in this photo is ignited. The pyrotechnic pellet in the rocket booster is ignited when enough forward momentum has compressed the spring to the right in this photo, driving a second primer onto a fixed firing pin. This is a timed and blocked event- the rocket motor ignition delay is separated from the primer flash channel by solid aluminum. The pellet burns in a set time to ignite the rocket booster when it reaches 11 meters in front of the launcher.

2) When the primer ignites, the expeller charge is fired off by the black powder in the center of the expeller tube. The expeller main charge propellant is double base NC/NG placed evenly around the central tube, in between the folded stabilizer fins. This is all wrapped with impregnated cardboard and a glued, waterproof tissue. This section is extremely vulnerable to moisture, so it is important to only remove from the carrying case just prior to firing. The expeller in an RPG-7 is now in an expansion chamber that is larger than the 40mm tube, so the expanding propellant gases rapidly build pressure and exert it onto the grenade.

3) At the rear of the expeller charge is a hard foam plug. As pressure builds in the expeller chamber, the grenade has forward pressure on it and eventually this plug breaks up and the parts of the plug and any unburnt cardboard are expelled out through the venturi and the blast cone. Directly in front of the plug is an aluminum turbine that imparts rotation immediately as the grenade shaft leaves the expeller chamber and tube.

4) As the grenade leaves the RPG tube, it has been “boosted” out by the expeller charge. Forward motion allows the four stabilizer fins to extend out to the sides, and it is important to remember this when firing as there must be at least 8 inches of clearance above all obstacles in the flight trajectory. This is also a good time to point out another reason not to install the expeller cartridge onto the rocket and carry it around. If this is bent or damaged then the entire trajectory may be thrown off. The pyrotechnic pellet will burn through to ignite the rocket booster, as long as the spring held block is out of the way due to proper forward momentum. Propellant gases begin the booster action at 11 meters from leaving the tube of the launcher.

5) The rocket motor burns and the gases push forward into the nozzle block expansion chamber at the front joint just behind the grenade body. This chamber has six holes that point to the rear and outward, and the pressure from the gases blows out the seals and the six holes drive the grenade assembly forward during its assisted flight. It is important to note that the holes are canted in a direction opposite that of the rotation imparted by the fins. The spin rate imparted by the four fins is slowed after rocket ignition. This prevents overspin, and reduces spin degradation of the shaped charge on firing. Just behind the nozzle block is an elastic ring that holds the RPG-7 round in the launcher so slight downward firing is possible without the round coming forward and misaligning the primer and firing pin. When the rocket burns out, forward momentum keeps the grenade airborne until it reaches a target or approximately 900 meters where the safety fuze causes the nose cone area to explode. This does activate the shaped charge, although this author has observed many RPG-7 rounds that reached the five second mark, the safety detonated, and the shaped charge was still intact.

6) Cutaway view of the shaped charge. The piezo-electric nose fuze fires a spark plug system at the rear of the shaped explosive content. As the detonation wave moves through the explosive, the tin coated copper cone at the center is transformed to a high-speed, high-temperature jet of metal that penetrates up to 13 inches of steel armor.

Arming

Firing sequence

Firing the RPG-7 series of weapons is considered a two man operation: the operator and assistant gunner. Both should be proficient with the system and should have a lot of live fire training. The skills needed to hit a target with an RPG can not be gained from simple training drills, especially firing at longer ranges. When the RPG team is “hunting,” it is just as important to figure in attempting to conceal their position and the backblast signature from the enemy as it is to find good front cover. In the case of needing a second shot, the backblast will frequently have located them for the enemy. Aiming so that the rear of the RPG-7 is pointed around the corner of a large building or hill can help with this. A couple of safety points should be emphasized. Behind the tube, for about 30 meters, there is a 70 degree danger zone. Close to the tube is a kill zone. The operator and his A-gunner should always be ensuring that there are no obstacles, walls, etc within 2 meters behind the RPG. Good advice would be to make that at least 3 meters. Blastback can be quite deadly. Firing from inside a small room is to be discouraged. We at SAR have been told that there exists a video clip of an Iraqi insurgent firing an RPG-7 from a third floor window with the backblast hurling him forward out the window. If you have this clip, please forward it to us. It contains sage wisdom for all potential operators.

The operator and A-gunner will have worked together and developed their own method of communicating these sequences, but it is advisable for the A-gunner to be on the left of the operator and reach across to load. This may not always be practical, but it is part of many countries’ training doctrine. Using today’s quality range finders is very important, as accurate range distance should increase first round hit probability. Once the pair have stalked their target, found range and target speed, and set up the firing position, the following sequence of events should occur:

• A-gunner visually clears the tube, then prepares the rounds to be fired, attaching the expeller charges.
• Operator ensures the push through safety is to the right and the hammer is not cocked, then announces “Load”.
• A-gunner loads a round into the tube, ensuring the index is properly occurring and the elastic gasket is snugly in place holding the round in the tube, then visually examines the backblast area for friendlies, to ensure there is no danger to the rear, and to ensure that various and assorted Operator and A-gunner appendages are out of the blast area. He announces “Clear to fire”.
• Operator announces “Ready” and the A-gunner removes the fuze protector and arms the grenade (this may have been done before loading). A-gunner resumes watching backblast area for friendlies and gives warning to the operator if the situation changes.
• Operator cocks the hammer, takes careful aim, pushes the safety to the left, then, squeezing the trigger, he fires. The operator then analyzes shot effect and decides whether to reload and repeat, or to depart the area with all due haste.
• In the event of a misfire, the operator announces “Misfire,” then pushes the safety to the right and “On,” announces “Safe” and the A-gunner makes a fast visual inspection to see if the grenade was properly indexed or not. High probability in a misfire will be that the grenade was not properly seated. If that is the case, the A- gunner then immediately reseats the grenade and initiates checks. Operator fires again. If the grenade was in place, then the A-gunner should pull the grenade forward and visually inspect the primer for a hit. If no hit, try again. If there is a dented primer, then the grenade should be gingerly moved away from the area and left for EOD (on the range) or blown in place at the first opportunity if in the field.
• If there is another misfire, then the A-gunner removes the grenade and inspects the primer. If there is no hit on the primer, then there must be a full check done on the pistol group and firing pin. The A-gunner should re-install the fuze cover and safety pin, then remove the round and unscrew and store the expeller charges and grenades in their carry cases. Under no circumstances should the expeller charges be left attached to the grenades and carried around. The reasons for this should be clear from the discussion of how the rounds work.

Defending against the RPG

A couple of quick notes on defending yourself against RPG-7 attacks. Unfortunately, for most vehicles it is not practical to put up any fencing around the vehicle. Perhaps the best defense is high speed and evasive maneuvering. Don’t drive one constant speed or straight path. The other helpful hint goes to suppressive fire – keep their heads down. If you are hit, remember that a back up shot will probably be coming soon – within 8-12 seconds.

When an RPG-7 is fired towards your position, there are three basic signatures. The first and second are simultaneous: the flash and 30 meter blast area behind the operator’s position, and the flash to the front of the operator (minimal). The third is that approximately 11 meters in front of the operator, there will be a larger puff of smoke where the rocket motor kicks in. This is generally quite visible and a good basis for aiming return fire. If you are in the line of fire, just aim back into the area and suppress. If you are oblique to the line of fire (e.g. the RPG was firing at a vehicle in front of you) aim back 11 meters from the puff and put the hammer down on your guns.

During the Vietnam War, US forces began building portable fencing structures on their vehicles. This was chain link fence or very tight barbed wire. The goal was two fold. First, the fence could catch the round in mid-flight, holding it and keeping it away from the vehicle. If the round then detonates it will not penetrate the armor. Most RPG-7 rounds are designed as shaped charges, so they need to be approximately two inches from the surface of the target when they go off, or they are ineffective. Rounds that have a self-destruct fuze will explode 5 seconds after firing, even if trapped in defensive fencing. This is a danger to soldiers who are unprotected. While the AT rounds are not designed as anti-personnel, there can be enough fragmentation and blast to kill or cause other casualties to those near the explosion. The second reason for the fencing is due to the manner in which the traditional RPG-7 rounds operate. There is a double cone in the front of the stand-off area. The space between the two cones is intended as the path for the peizo electric fuze to ignite the main fuze on the shaped charge. It is quite effective, but if the round strikes the fencing and this cone area is distended and broken, the fuze can’t operate. Newer rounds have a bypass system in place so the best the defender can hope for is to hold the round in fencing, away from the skin of the vehicle, when it explodes. Damage to unprotected personnel can be expected. In the event that the nose fuze strikes a strand of the fence, the round will detonate away from the vehicle, nullifying the shaped charge effect.

Armorer’s Hints for the RPG-7 Series and the RPG-2

Disassembly of the RPG series at the operator level is confined to removal of the trigger group, the heat shields, scope, and performing inspection and maintenance on these items. There are a number of cleaning tools supplied including a large brush and swab. The interior of the tube is chromium lined but needs frequent cleaning during use due to the corrosive nature of the powder in the expeller charge, as well as how the expeller charge operates. The charge has paper, foam, and burning propellant that is supposedly expelled through the venturi and to the rear, but on occasion particles remain that can either block the next round from being properly inserted, or lead to corrosion. Once the tube is cleaned, a very, very, light coat of oil should be applied internally.

Firing Pin

The firing pin location and projection are key to the operation of these systems – and are very basic. There is a double headed pin with a barrel body, which is held in a well in the bottom side of the launcher. One pin is smaller and is the firing pin. The other larger diameter pin is for the hammer to strike. The firing pin hole in the body is aligned with where the primer on the grenade body should be. Any misalignment or change in the extension of the firing pin into the primer will affect the reliability of the firing sequence. The firing pin is held in position by two pieces: a cup that is replaceable and locates the pin in the well, and a threaded plug that holds it into the well. The plug has a hole in it that mirrors the firing pin hole, allowing the striking end of the firing pin to face the hammer. The central body of the firing pin has a spring coiled around it, which keeps the firing pin from entering the firing pin hole unless the hammer has struck it.

Disassembly of Trigger Group

Most shooters will recognize the internal parts design from numerous single shot hammer fired rifles and shotguns. The design is not unusual. The group is held in position by a fixed lug at the rear and a push through split takedown pin at the front. In the case of the B-40, the front is frequently held in by a screw. There are other variations and removal should be obvious by what method is used. There is a push-through trigger blocking safety, and the hammer is manually cocked. Once cocked, the safety is engaged; left to right from the operator’s view is “Safe” and pushing through from right to left is “Fire.” This can be accomplished using the inside of the index finger, which rests in that area when holding the grip. When the hammer is cocked, the sear engages it and holds it under spring tension from the hammer spring. Once the safety is off, and the trigger pulled, the hammer moves rapidly upward under tension, but it is the momentum of the hammer itself that causes it strike the firing pin. The hammer spring is mechanically kept from forcing the hammer all the way to the top of its cycle. There would be too much force in that case, thus the mechanical block. The cycle repeats.

Disassembly is in the following manner, with one exception. The early RPG-2 and B-40 type trigger groups may have the pin hole for the hammer spring removal in such a manner that the pivot and spring must be removed under pressure. Early armorers had a program to drill out a straight well so that once contained under pressure, the spring could be removed in that contained state and replaced on reassembly.

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