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7.62 × 42 mm SP-4

Category
Ammunition, Missiles and precision weapons
The 7.62 × 42 mm SP-4 is a synonyms 7.62 × 42 mm; 7.62 mm silent cartridge Armament TsNIITOCHMash PSS semi-automatic pistol; NRS-2 Special Scout Knife Development The 7 × 42 mm SP-4 cartridge was developed for use in the PSS, a small semi-automatic silent pistol. Little is known of the development history of the SP-4 , other than the fact that it was developed in conjunction with the PSS pistol to provide a compact silent firearm that did not require a bulky external suppressor. Description The SP-4 case is of
drawn steel, copper washed, of conventional rimless design, with a slight taper and small bottleneck except that the case walls are very thick to retain the propellant gases and provide obturation of the internal piston. No manufacturer's headstamp has ever been encountered with this cartridge, so the manufacturer is unknown. The SP-4 is Berdan primed. The bullet is a low alloy steel cylinder with a reduced diameter at the front which is splined and has a brass rotating or driving band swaged over it. The rear of the bullet has a central conical recess, which mates with the top of the driving piston and centralises the bullet in the case and in the pistol bore as it is fired. The projectile is lubricated with a dry molybdenum sulphide coating. The bullet body diameter is 7.59 mm; rotating/driving band diameter is 7.8 mm and overall projectile length is 28.4 mm. On firing, the primer ignites the propelling charge which drives the piston forward, pushing the bullet into the bore of the pistol and engaging the rotating/driving band with the rifling. The piston stops against the internal case shoulder and deforms slightly, thereby sealing the gases inside the case. RUSSIAN FEDERATION Manufacturer State Arsenals Type: Ball: Steel; 9.97 g; V o 300 - 310 m/s.