5.45×39mm

5.45×39mm
5.45×39mm cartridge
Type	Rifle
Place of origin	Soviet Union
Service history
In service	1974–present
Used by	Soviet Union/Russian Federation, former Soviet republics, former Warsaw Pact
Wars	Afghan War, Georgian Civil War, First Chechen War, Second Chechen War, Yugoslav Wars, Syrian civil war
Production history
Designed	early 1970s
Specifications
Case type	Steel, rimless, bottleneck
Bullet diameter	5.60 mm (0.220 in)
Neck diameter	6.29 mm (0.248 in)
Shoulder diameter	9.25 mm (0.364 in)
Base diameter	10.00 mm (0.394 in)
Rim diameter	10.00 mm (0.394 in)
Rim thickness	1.50 mm (0.059 in)
Case length	39.82 mm (1.568 in)
Overall length	57.00 mm (2.244 in)
Case capacity	1.75 cm3 (27.0 gr H2O)
Rifling twist	255 mm (1 in 10 inch) or 200 mm (1 in 7.87 inch)
Primer type	Berdan or Small rifle
Maximum pressure	380.00 MPa (55,114 psi)
Ballistic performance
Bullet mass/type Velocity Energy 3.43 g (53 gr) 7N6 FMJ mild steel core 880 m/s (2,900 ft/s) 1,328 J (979 ft·lbf) 3.43 g (53 gr) 7N6M FMJ hardened steel core 880 m/s (2,900 ft/s) 1,328 J (979 ft·lbf) 3.62 g (56 gr) 7N10 FMJ enhanced penetration 880 m/s (2,900 ft/s) 1,402 J (1,034 ft·lbf) 3.69 g (57 gr) 7N22 AP hardened steel core 890 m/s (2,900 ft/s) 1,461 J (1,078 ft·lbf) 5.2 g (80 gr) 7U1 subsonic for silenced AKS-74UB 303 m/s (990 ft/s) 239 J (176 ft·lbf)
Test barrel length: 415 mm (16.3 in) and 200 mm (7.9 in) for 7U1 Source(s):

The 5.45×39mm cartridge is a rimless bottlenecked rifle cartridge. It was introduced into service in 1974 by the Soviet Union for use with the new AK-74 assault rifle. It gradually supplemented, then largely replaced the 7.62×39mm round in service.

The 5.45×39mm cartridge was developed in the early 1970s by a group of Soviet designers and engineers under the direction of M. Sabelnikov. Further group members were: L. I. Bulavsky, B. B. Semin, M. E. Fedorov, P. F. Sazonov, V. Volkov, V. A. Nikolaev, E. E. Zimin and P. S. Korolev.

The 5.45×39mm is an example of an international tendency towards relatively small-sized, lightweight, high-velocity military service cartridges. Cartridges like the 5.45×39mm, 5.56×45mm NATO and Chinese 5.8×42mm allow a soldier to carry more ammunition for the same weight compared to their larger and heavier predecessor cartridges, have favourable maximum point-blank range or "battle zero" characteristics and produce relatively low bolt thrust and free recoil impulse, favouring lightweight arms design and automatic fire accuracy.

The Soviet original military issue 7N6 cartridge variant introduced in 1974 are loaded with full metal jacket bullets that have a somewhat complex construction. The 3.43 g (52.9 gr) boat-tail projectile's jacket is clad in gilding metal. The unhardened 1.43 g (22.1 gr) steel (steel 10) rod penetrator core is covered by a thin lead inlay which does not fill the entire point end, leaving a hollow cavity inside the nose. The bullet is cut to length during the manufacturing process to give the correct weight. The 7N6 uses a boat-tail design to reduce drag and there is a small lead plug crimped in place in the base of the bullet. The lead plug, in combination with the air space at the point of the bullet, has the effect of moving the bullet's center of gravity to the rear; the hollow air space also makes the bullet's point prone to deformation when the bullet strikes anything solid, inducing yaw. The brown-lacquered steel case is Berdan primed. Its 39.37 mm (1.55 in) length makes it slightly longer than the 7.62×39mm case which measures exactly 38.60 mm (1.52 in). The primer has a copper cup and is sealed with a heavy red lacquer. The propellant charge is a ball powder with similar burning characteristics to the WC844 powder used in 5.56×45mm NATO ammunition. The 7N6 cartridge weight is 10.75 g (165.9 gr).