The PSS silent pistol (official GRAU index 6P28) is the last completed weapon system resulting from the Soviet development of silent pistols operating on a sealed cartridge 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. Intended for assassinations and reconnaissance, it was produced in the special weapons foundry at Tznitochmash. 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 reconnaissance and assassinations. The weapon uses a unique cartridge with an internal piston to achieve this end. Otherwise, it is a fairly simple double action pistol. Few details are known about the pistol's performance, as only a few have entered western hands.
The PSS uses a specially developed 7.62x42mm necked round. The cartridge 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 "reaction", due to there being no blast indicative of a blowback action.