Military 7.62mm NATO Versus Soviet 7.62x39mm
Q: What is the velocity of military 7.62mm ball ammunition? How does it compare with the 7.62x39mm Russian round and military 5.56x45 NATO ammo?
A: When fired from a standard M14 rifle, the 7.62 NATO ball 149gn FMJ boattail bullet has a muzzle
velocity of 2800fps and muzzle energy of 2594 ft/lbs. When fired from a standard AKM rifle, the 122gn Soviet round has a muzzle velocity of 2340fps and energy of 1483 ft/lbs. When fired from a standard M16A1E1 rifle, the SS109 62gn FMJ boattail with steel penetrator (.223 Ball) has a muzzle velocity of 3050fps and energy of 1281 ft/lbs.
At 300 yards, the numbers are 2159fps and 1542 ft/lbs for the 7.62NATO, 1606 fps and 699 ft/lbs for the 7.62x39 Soviet and 2220 fps and 679 ft/lbs for the 5.56 NATO round. The Soviet 5.45x39 cartridge, introduced in 1974 for use in the new AK-74 Assault rifle fired a 54gn spitzer bullet at 2950fps for 1045 ft/lb of muzzle energy.
Warning. My data on current military rifles for these cartridge is probably somewhat dated.