5.45x39mm
From Wikipedia, the free encyclopedia
| 5.45x39mm M74 | ||
|---|---|---|
 |
||
| Type | Rifle | |
| Place of origin |  Soviet Union |
|
| Service history | ||
| In 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 | |
| Production history | ||
| Designed | 1972 | |
| 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 | 10.0 mm (0.394 in) | |
| Rim diameter | 10.0 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) | |
| Rifling twist | 255 mm (1 in 10 in) | |
| Primer type | Berdan, small rifle | |
| Maximum pressure | 380.0 MPa (55,114 psi) | |
| Ballistic performance | ||
| Bullet weight/type | Velocity | Energy |
| 50 gr (3.2 g) 5N7 FMJ | 915 m/s (3,000 ft/s) | 1,316 J (971 ft·lbf) |
| Test barrel length: 415 mm (16.6 in) |
||
The Soviet 5.45x39mm round was introduced into service in 1974 for use with the new AK-74 assault rifle. It gradually supplemented and then largely replaced the 7.62x39mm round in service.
Contents |
[edit] Design details
The Russian military issue 5N7-specification 5.45mm bullets are a somewhat complex full metal jacket design. The 56 gr (3.6 g) boattail projectile has a gilding-metal-clad jacket. The unhardened steel core is covered by a thin lead coating 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 base of the bullet is tapered 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 7.62x39mm casing 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 WC 844 powder used in 5.56x45mm NATO ammunition.
The 50 gr (3.2 g) tracer projectile has a shorter ogival profile and is green-tipped. The amount of igniter material provides for a burn of up to 800 m.
[edit] Cartridge dimensions
The 5.45x39mm has 1.75 ml (27 grains H2O) cartridge case capacity.
5.45x39mm maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm).[1]
Americans would define the shoulder angle at alpha/2 ≈ 20.3 degrees. The common rifling twist rate for this cartridge is 255 mm (1 in 10 in), 4 grooves, Ø lands = 5.60 mm, Ø grooves = 5.40 mm, land width = 2.60 mm and the primer type is either berdan or small rifle.
According to the official C.I.P. (Commission Internationale Permanente Pour L'Epreuve Des Armes A Feu Portative) guidelines the 5.45x39mm case can handle up to 380 MPa (55,114 psi) piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers.
[edit] Wounding effects
A: projectile jacket
B: steel core
C: hollow point
D: lead inlay
E: propelling charge
Early ballistics tests done demonstrated a pronounced tumbling effect with high speed cameras.[2] Some Western authorities believed this bullet was designed to tumble in flesh to increase wounding potential. At the time, it was believed that yawing and cavitation of projectiles was primarily responsible for tissue damage. Martin Fackler conducted a study using live pigs and ballistic gelatin demonstrating that the 5.45 mm round does not reliably fragment or cause unusual amounts of tissue disruption. [3] 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.
[edit] Bullet construction
As body armor saw increasing use in Western militaries, bullet construction was changed several times to compensate. In 1987 a steel rod in the original 7N6 bullets was hardened to 60 HRC. In 1992 the size of the steel penetrator was increased and the lead plug in front of it discarded. This bullet was designated 7N10 "improved penetration". In 1994 the 7N10 design was improved by filling the air space with lead. Upon impacting a hard target, soft lead is pressed sideways by the steel penetrator, its hydrostatic pressure tearing the jacket. The 7N22 armour-piercing bullet, introduced in 1998, has a sharp-pointed steel penetrator and retaining the soft lead plug in the nose for jacket discarding. [4] The recent 7N24 "super-armor-piercing" bullet has a penetrator made of tungsten carbide.
[edit] References
- ^ C.I.P. decisions, texts and tables free current C.I.P. CD-ROM version download (ZIP and RAR format)
- ^ "Terminal ballistics of the Russian AK 74 assault rifle: Two wounded patients and experimental findings". http://findarticles.com/p/articles/mi_qa3912/is_200112/ai_n9010648/pg_3. Retrieved on 2007-09-25.
- ^ "Wounding Potential of the AK-74 Assault Rifle". http://www.btammolabs.com/fackler/ak74_wounding_potential.pdf. Retrieved on 2007-09-25.
- ^ "Evolution of the 5,45 mm bullet". http://grigorew.narod.ru/raznoe/kal545.htm.
