Not to be confused with 7.62x51mm NATOThe 7.62x39mm cartridge is a Soviet rifle round. It was used in many Kalashiknov-type assault rifles.
In a cringe-inducing scene from Rambo III, Rambo takes a 7.62 from an AK-47 magazine, cuts the bullet off of the casing and then empties the gunpowder into a shrapnel wound in his torso before lighting it on fire, painfully cauterizing it.
The 7.62×39mm round was designed during World War II. It was first used in the RPD machine gun. Due to the worldwide proliferation of the SKS and AK-47 pattern rifles, the cartridge is used by both militaries and civilians alike. 7.62×39mm ammunition is purportedly tested to function well in temperatures ranging from −50 °C (−58 °F) to 50 °C (122 °F) cementing its usefulness in extremely cold polar or hot desert conditions. The 7.62×39mm cartridge was influenced by a variety of foreign developments, including the German Mkb 42(H) and the U.S. M1 carbine.
Shortly after the war, the world's most recognized military pattern rifle was designed for this cartridge: the AK-47. The cartridge remained the Soviet standard until the 1970s, and is still one of the most common intermediate rifle cartridges used around the world. It was replaced in Russian service by the faster and smaller 5.45×39mm cartridge, which is used by the current issue AK-74 and variants. However, 5.45 still outperforms 5.56 because it uses velocity and ballistics together. 5.45 has been known to take off limbs as a result of detrimental ballistics.
While the 5.56mm NATO was designed to maim enemies, the 7.62 was designed to kill them. Ballistics tests have shown that the 7.62 is much more powerful and detrimental than the 5.56. In a cinderblock test, the 5.56 punched a neat hole through the first side of the block, while the 7.62 completely destroyed the first half of the block, pulverizing it into dust and chunks. Nonetheless, it was very slow, since it had been designed for close-quarters combat. So, the Soviets designed the 5.45x39mm to compete with the American 5.56mm NATO, although the 5.45 was far more deadly than the 5.56 as well. 5.45 was designed with steel-core bullets, so they have been known to take off limbs and use velocity to its advantage, rather than 5.56, which was designed to get lodged in bones and injure the person. 5.45 was still designed to kill, keeping with Soviet efficiency.