The Soviet 5.45 × 39 mm M74 round was introduced into service in 1974 in the AK-74 assault rifle, an updated version of the AK-47, and the AKSU-74 carbine/sub-machine gun. The round, which replaced the 7.62 × 39 mm round then in Soviet service, was likely developed based on Soviet observation of the American 5.56 × 45 mm round in Vietnam. 1974 (MCMLXXIV) was a common year starting on Tuesday (the link is to a full 1974 calendar). ... AK74 assault rifle The AK-74 assault rifle is the modernized version of the AK-47 developed in 1974, chambered in a smaller cartridge (5. ... The AK-47 is the iconic assault rifle. ... Avtomat Kalashnikova model 1947 g. ... The AKSU-74 (also referred as AKS-74U or AK-74SU ) was introduced in 1970s. ... This article or section should include material from Soviet M1943 The Soviet 7. ... U.S. Military 5. ...

The Russian military-issue 5N7 specification 5.45 mm bullets are a somewhat complex full metal jacket design. Some people have said that the Russians were concerned about the lower energies of the bullets and designed them to cause more damage than might otherwise occur. The bullet's core consists mainly of a length of soft steel rod, cut to length during the manufacturing process to give the correct weight. There is a hollow air space underneath the bullet's thin copper jacket ahead of the steel rod core. The base of the bullet is tapered, to reduce vacuum drag (a so-called boat-tail bullet) and there is a small lead plug crimped in place in the base of the bullet, ostensibly so that the thin copper alloy jacket material can be stamped in place in the proper tapered shape. The lead plug, however, in combination with that air bubble in the point of the bullet, has the effect of pushing the bullet's center of gravity very far to the rear, and the hollow air space under the point of the bullet makes the bullet's point prone to bending to one side when the bullet strikes anything solid, unbalancing it. Most authorities in the West believed this bullet was designed specifically to tumble in flesh, which should have increased wounding potential. A full metal jacket bullet (or FMJ) is a bullet that is encased in a copper-coated steel or gilding metal jacket. ... For a solid object moving through a fluid or gas, drag is the sum of all the aerodynamic or hydrodynamic forces in the direction of the external fluid flow. ...

At the time, it was mistakenly believed that yawing and cavitation of projectiles was of major importance in producing tissue damage. Although Dr. Fackler later showed that projectile fragmentation was the key to producing significant wounding effect, this was unknown to the Soviets when they began development of the new round. This was similarly unknown to the non-Soviet alarmists who feared that they had achieved wounding parity with the 5.56mm M16 round.

Unfortunately, the rigidity of the bullet prevented it from fragmenting and the round soon developed a reputation for being a mediocre stopper. Reports of the 5.45 projectile producing horrific wounds have been repeatedly demonstrated to be false. In his terminal ballistics study using live pigs and ballistic gelatin (1984), Fackler was able to demonstrate that the AK-74, even at close range, did no more damage than a handgun round. The only exception was a hit to the liver, which caused heavy damage due to the stiffness of the organ. All other organs and tissue were too flexible to be severely damaged by the temporary stretch effect.

With the 5.45 mm bullet, the tumbling produced a temporary stretch cavity twice, at 100 and 400 mm of depth. This is comparable to modern 7.62x39 ammunition and to tungsten penetrator (non fragmenting) 5.56 ammunition. The average width of a human trunk is 400 mm.

Specifications

• Bullet weight: 3.25 g
• Muzzle velocity: 900 m/s
• Muzzle energy: 1,316 J