The RPG-7 System Primer

The RPG-7 System Primer

View of cutaway RPG-7 HEAT round. On the right, the outer ribbed cone is the standoff, and it creates the outer path of the ignition circuit that continues the entire length of the warhead. Just underneath it, observe the inner cone that creates the inner electrical path. The space between them is an open air insulator area. This is the section that chain link fence defenses are intended to fracture, short circuit and disrupt.

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.

In this cutaway view, we can see that the firing pin at rest does not enter the tube, and when it does, the proper firing pin protrusion that it is capable of. This does not mean this is the proper firing pin protrusion when firing, just that it has not been interfered with. Since the hammer is under its own momentum when it strikes the firing pin and not under hammer spring pressure, the firing pin receives just enough pressure to solidly strike the primer. This obviously can not be seen in a complete launcher, but a quick view from the front looking down the empty tube towards a light surface will show whether the pin is operating properly. Press the firing pin in from the hammer view to ensure there is spring resistance. If no resistance, replace the spring.
LEFT: The firing pin plug is squared into its well when properly threaded into place. This is on an RPG-7D. RIGHT: Firing pin plug has been threaded out using a common wrench. Damage can be seen on the plug from previous operators using improper tools that slipped off. The plug should be replaced in this condition. A very light coating of anti-seize compound should be applied to these threads.

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.

Left to Right: Firing pin plug, firing pin with spring, firing pin cup. All parts should be inspected for wear, chipping, or breakage.

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 to 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.

Tip for reassembly: Once you have the cup, the firing pin and spring, and the plug in place, and have started threading the plug in, use a pin punch to ensure the firing pin can travel all the way in. Then, holding the punch in place, thread the plug in around it. Snug the plug square and just beyond hand tight.

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.

SADJ would like to thank Paul Newhouse and Richard Jones for their help in this article.