5.45x39mm

Infobox Firearm Cartridge
name=5.45x39mm M74


caption=
origin=flagcountry|Soviet Union
type=Rifle
service=1974-present
used_by=Soviet Union/Russian Federation, former Soviet republics
wars=Afghan War, Georgian Civil War, First Chechen War, Second Chechen War, Balkan Wars
variants=
is_SI_specs=yes
parent=
case_type=Steel, rimless, bottleneck
bullet=5.680
neck=6.248
shoulder=7.290
base=10.033
rim_dia=10.008
rim_thick=1.372
case_length=39.624
length=56.388
rifling=
primer=Berdan, small rifle
is_SI_ballistics= yes
bw1= 50
btype1=5N7 FMJ
vel1=915
en1=1316
bw2=
btype2=
vel2=
en2=
bw3=
btype3=
vel3=
en3=
bw4=
btype4=
vel4=
en4=
bw5=
btype5=
vel5=
en5=
test_barrel_length=415 mm (16.6 in)
balsrc= The Soviet 5.45x39mm round was introduced into service in 1974 for the AKS-74U and the AK-74 assault rifle. It gradually supplemented then largely replaced the 7.62x39mm round then in service.

Design

The Russian military issue 5N7-specification 5.45 mm 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 ahead of the steel rod behind the bullet tip. The base of the bullet is tapered to reduce drag (a boat-tail bullet) 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.

Wounding effects

Early ballistics tests done demonstrated a pronounced tumbling effect with high speed cameras. [cite web |url=http://findarticles.com/p/articles/mi_qa3912/is_200112/ai_n9010648/pg_3 |title=Terminal ballistics of the Russian AK 74 assault rifle: Two wounded patients and experimental findings |accessdate=2007-09-25 ] Some Western authorities believed this bullet was designed to tumble in flesh to increase wounding potential. demonstrating that the 5.45 mm round does not reliably fragment or cause unusual amounts of tissue disruption. [cite web |url=http://www.btammolabs.com/fackler/ak74_wounding_potential.pdf |title=Wounding Potential of the AK-74 Assault Rifle |accessdate=2007-09-25 ] Most organs and tissue were too flexible to be severely damaged by the temporary cavity effect caused by yaw and cavitation of a projectile. With the 5.45 mm bullet, tumbling produced a temporary cavity twice, at depths of 100 and 400 mm. This is comparable to modern 7.62x39mm ammunition and to (non-fragmenting) 5.56 mm ammunition. The average width of a human trunk is 400 mm.

Anti-armor effect

As body armor saw increasing use in Western military forces, bullet construction was changed several times to keep it up with improving means of ballistic protection. In 1987 a steel rod of original design 7N6 bullets was hardened to 60 HRC. In 1992 size of the steel penetrator was increased, and lead plug in front of it discarded (still there was some empty space under the jacket in the bullet's nose), this bullet designated as 7N10 "improved penetration". In 1994 the 7N10 design was improved by filling nasal empty space with lead again. At the impact at hard target soft lead is pressed sideways by following steel penetrator, its hydrostatic pressure tearing the jacket, so the penetrator goes in clear of jacket, being able to penetrate more. In 1998 a new design was introduced - a 7N22 armour-piercing bullet with sharp-pointed steel penetrator made of special steel, still with soft lead plug in the nose for jacket discarding. [cite web |url=http://grigorew.narod.ru/raznoe/kal545.htm |title=Evolution of the 5,45 mm bullet ] A newest known design is 7N24 "super-armor-piercing" bullet with penetrator made of tungsten carbide, but due to higher cost it's doubtful that 7N24 would be fielded in large scale.

pecifications

*Bullet weight: 3.43 g (7N6), 3,61 g (7N10), 3,69 g (7N22), about 4 g (7N24), 5,15 g (7U1 subsonic for use with silencer)
*Muzzle velocity: 915 m/s (7N6?)
*Muzzle energy: 1,316 J (7N6?)

References

Notes and Citations

* Fackler ballistics study - [http://www.btammolabs.com/fackler/ak74_wounding_potential.pdf]
* Terminal Ballistics Study - Bosnia - Military Medicine/December 2001 [http://www.findarticles.com/p/articles/mi_qa3912/is_200112/ai_n9010648]
* Photos of various different types of 5.45x39mm ammunition [http://www.conjay.com/Ammunition%20for%20Armor%20Testing%20East%205.45mm%20x%2040.htm]