5.45×39mm

The Soviet 5.45x39mm round was introduced into service in 1974 for the AKS-74U and the AK-74 assault rifle. It replaced the 7.62x39mm round then in service.

The Russian military issue 5N7-specification 5.45mm bullets are a somewhat complex full metal jacket design. 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. The base of the bullet is tapered, to reduce vacuum drag (a 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 the 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. Early ballistics tests done showed the tumbling effect with high speed cameras.^[1] Because of this, some Western authorities believed this bullet was designed to tumble in flesh to increase wounding potential.

At the time, it was mistakenly believed that yawing and cavitation of projectiles was of major importance in producing tissue damage. Although Dr. Martin 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.^{[citation needed]} This was similarly unknown to the non-Soviet alarmists who feared that they had achieved wounding parity with the 5.56 x 45mm NATO round.

However, the rigidity of the 5.45mm bullet prevents fragmentation and gave it a reputation for being a mediocre stopper.^{[citation needed]} Reports of the 5.45mm projectile producing horrific wounds have been repeatedly demonstrated to be false.^{[citation needed]} In his terminal ballistics study using live pigs and ballistic gelatin, Fackler was able to demonstrate that the 5.45mm round does not fragment or cause unusual amounts of tissue disruption. ^[2] The only exception was a hit to the liver, which caused heavy damage due to the rigidity of the organ tissues. All other organs and tissue were too flexible to be severely damaged by the temporary cavity effect.

With the 5.45mm bullet, the tumbling produced a temporary cavity twice, at depths of 100 and 400mm. This is comparable to modern 7.62x39mm ammunition and to tungsten penetrator (non-fragmenting) 5.56mm ammunition. The average width of a human trunk is 400mm.

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

• Fackler ballistics study - [1]
• Terminal Ballistics Study - Bosnia - Military Medicine/December 2001 [2]
• Photos of various different types of 5.45x39mm ammunition[3]