SP-4 silenced ammunition
The key problem with the SP-3 and PZAM ammo were their telescoped pistons, which projected significantly from fired cases and thus made almost impossible to develop the semi-automatic weapons for these cartridges. During late 1970s and early 1980s soviet designers solved this problem by developing the 7.62x42 SP-4 ammunition, which used the same basic principle. The telescoped two-stage piston has been replaced by single-stage piston, which did not projected from the case when fired; the standard 7.62mm M43 bullet has been replaced by the cylindrical bullet, made of mild steel, and fitted with a brass driving band at the front. This cartridge has been adopted circa 1983 by KGB and Spetsnaz elements of the Soviet Army, along with six-shot, magazine fed, blowback operated semiautomatic PSS pistol and single-shot NRS-2 scout shooting knife. The SP-4 ammunition and PSS pistols are still in use by elite Spetsnaz units within Russian armed forces, as well as by some FSB and MVD elite units. Apparently, the earlier MSP pistol with SP-3 ammo and SP-4M pistol with PZAM ammo were not phased out of service and still can be encountered in the hands of serious operators, who not require multi-shot capabilities of PSS / SP-4 system.
cartridge metric designation bullet weight muzzle velocity
SP-4 7.62x41 9,3 g / 143 grain 270 m/s / 885 fps
