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 somewhat complex optical sight. SADJ 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 in a regular force are dedicated to this job and do receive a lot of training. (So people should definitely train with the optics). 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 U.S., it is difficult to get this experience due to our importation laws on explosives and the fact that the U.S. military has a very wise policy of not allowing the firing of captured ammunition of this type. (In the event that there are U.S. end users reading this who need to arrange live fire training outside the U.S., please contact Long Mountain Outfitters at www.longmountain.com.) Other military users probably have better access to live rounds.
There are many, many rounds on the market today. SADJ 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 PG-7V.
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. Some sources state that this event occurs between 5 and 20 meters. This is incorrect. The event must be a repeatable performance for accuracy, and the Russian, Chinese, Bulgarian, Romanian, etc., manufacturers are well aware of this and critical quality control is exercised in these fuzes. Manufacturers will target 10 to 15 meters for rocket assist ignition, attempting to keep their lots consistent. Initial design calls for 11 meters. If the ignition point is inconsistent from round to round, target acquisition will not be repeatable. Large deviations in that distance usually indicate improper storage and degradation of fuze train.
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 section placed in an RPG-7 is 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 at a pre-determined pressure, 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.