BULLET TYPE – Round nose full metal jacket with duralumin “stem” (base pusher)
BULLET DIAMETER – 7.90 mm (0.311 in)
BULLET WEIGHT – 6.2 g (96 grains)
POWDER WEIGHT – 0.15 g (2.31 grains)
CASING WEIGHT – 5.18 g (80 grains)
TOTAL ROUND WEIGHT – 11.6 g (179 grains)
MUZZLE VELOCITY – 175 m/s (574 fps)
NOMINAL BARREL LENGTH – 2.5 cm (1 in)
MUZZLE ENERGY – 95 J (70 ft/lb)
This was the first Soviet captured piston round to see success. It was developed from the earlier (1953) SP-1 round which suffered from casing cracks and other failures. When the SP-2 round was developed, further work on the SP-1 round was ended. The round resembles a 7.62x39mm M43 casing, shorted and loaded with the bullet from a 7.62x25mm Tokarev round. The bullet itself is little more than a bullet jacket with a hollow core, fitted with a short aluminum rod. The very small propellant charge is held against the primer by a metal cup. When fired, the cup drives against the aluminum rod, pushing it out from the cartridge casing. Once the propellant cup strikes the bottleneck of the cartridge case, it is stopped and seals the propellant gases behind it. The projectile is driven forward, through a very short rifled barrel, on to the target. The projectile has the power to strike through nearly 4 cm (1.5 inches) of wooden planks at 5 meters range. With the propellant gases sealed within the cartridge case, the sound of firing the SP-2 round is very quiet, only slightly louder than tapping a fingernail against a table top.
