The PSS uses a specially developed 7.62×41mm necked round SP-4 (СП-4), also used by the
OTs-38 Stechkin silent revolver. The
cartridge contains a propelling charge which drives an internal piston in contact with the base of the bullet. On firing, the piston propels the bullet out of the barrel with enough energy to achieve an effective range of 25 meters. At the end of its travel, the piston seals the cartridge neck, preventing noise, smoke, or blast from escaping. == Action ==