Basic Information
Usually when people want a silent firearm they take an existing weapon, fit a suppressor and use cold loaded ammunition to make it quieter. Sometimes they build a weapon from the ground up to be quieter and get something like the de Lisle carbine. These are the common strategies and they both work … to varying degrees … but very rarely suceed in completely silencing the gunshot.
For that, you need something like a silent cartridge. These are rare beasts, complicated to engineer and usually more trouble than they are worth, but a useful technology to possess. The Soviet Union has particularly fond of them and came out with several designs which should be considered typical of the concept.
Broadly, a typical silent cartridge design operates by trapping all of the explosion from the round within the case - when the propellant fires it drives a piston, which expells the bullet from the case and then seals the gap behind it, ensuring that no gas escapes from the cartridge. Thus there is no blast, no flash - no sound at all except for the sound of the weapon's action and the passage of the bullet … and a subsonic bullet will be virtually silent in flight.
The Soviet S4M derringer is a classical example - and application - of the technology: - a two shot, break open weapon that fired the bullet from a 7.62mmWarPac round from a silent cartridge along a barrel designed to leave rifling marks identical to those of an AK47/AKM. This would leave anyone examining the body of someone shot with the weapon in question with the impression that the dead person had been hit from a long distance with an AK (due to the low impact velocity) rather than very short range with a pistol. Only of very limited use, but very useful in a limited field. Having developed the technology, the Soviets used it in all sorts of things, including the NRS-2 commando knife.
One of the weirder silent cartridges to be developed was the American M463 - a 40mm round, originally for the M79 grenade launcher which was fired almost silently and without smoke or muzzle flash by the abovementioned piston system … and effect somewhat spoilt by its high explosive payload, but at least the weapon could be fired at night, leaving the enemy with only a mysterious explosion to let them know they were under attack. Along the same lines the French LGI Mle F1 light mortar also uses a closed piston cartridge, with a measured firing signature of ~52dBA (less than that of typical conversation) - again, the round still explodes on landing, and rate of fire is reduced by the need to remove the spent cartridge after firing, but the firing position is made very hard to locate.
Sources
Game and Story Use
- The S4M is worth noting in its own right, especially for a CSI style campaign … and the design philosophy could easily be resurrected by someone else with forensics experts to annoy.
- Mossad would be obvious suspects, except they generally like their targets to know who has just attacked them.
- A silent cartridge/derringer combination would likely make a good assassination or insurgency weapon, designed either to eliminate a target in (relatively) secure locations or to allow an insurgent to quietly eliminate an enemy soldier or policeman and accquire his weapon.