The PSS silent pistol (official GRAU index 6P28) is the last completed weapons system resulting from the Soviet development of silent pistols operating on a sealed cartrige system. Two previous designs were considered unacceptable for use due to their limitation to two shots. Earlier systems included the MSP and SP-4M double barreled pistols. Developed around 1980, the PSS was first issued to KGB Spetsnaz in 1983, and was intended for assassinations and reconaissance. PSS pistols are still in use by elite special forces units of many nations, as well as by some FSB, MVD, and KGB elite units.
The PSS was developed to give Soviet special forces and secret police an almost completely silent option for covert operations such as reconaissance and assassinations. The weapon uses a unique cartrige with an internal piston to achieve this end. Otherwise, it is a fairly simple double action pistol.
The PSS uses a specially developed 7.62x42mm necked round. The cartrige contains an internal piston and a propelling charge, with the stem of the piston against the base of the bullet. On firing, the piston delivers enough impulse to project the bullet from the barrel to an effective range of 25 meters. The piston then seals the cartridge neck, preventing noise, smoke, or blast from escaping the barrel.
The action of the PSS can be described as a "reaction" due to there being no blast indicative of a blowback action.