5.45x39mm
| 5.45x39mm Cartridge | 5.45x39mm Ballistics tables | Cartridges |
| 5.45x39mm M74 | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
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| The 5.45 Soviet cartridge. | ||||||||||
| Type | rifle | |||||||||
| Country of Origin | USSR | |||||||||
| Specifications | ||||||||||
| Case Type | Steel, rimless, bottleneck | |||||||||
| Bullet Ø | 5.680 mm (0.2236 in) | |||||||||
| Neck Ø | 6.248 mm (0.2460 in) | |||||||||
| Shoulder Ø | 7.290 mm (0.2870 in) | |||||||||
| Base Ø | 10.033 mm (0.3950 in) | |||||||||
| Rim Ø | 10.008 mm (0.3940 in) | |||||||||
| Rim Thickness | 1.372 mm (0.0540 in) | |||||||||
| Case Length | 39.624 mm (1.5600 in) | |||||||||
| Full Length | 56.388 mm (2.2200 in) | |||||||||
| Primer | Berdan, small rifle | |||||||||
| Production & Service | ||||||||||
| In Service | 1974-present | |||||||||
| Used By | Soviet Union/Russian Federation, former Soviet republics | |||||||||
| Wars | Afghan War (Soviet), Georgian Civil War, First Chechen War, Second Chechen War, Balkan Wars | |||||||||
| Ballistic Performance Sampling | ||||||||||
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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.
Contents |
History
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 and produce relatively low bolt thrust and free recoil impulse, favouring lightweight arms design and automatic fire accuracy.[1]
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).
Tests indicate the free recoil energy delivered by the 5.45×39mm AK-74 assault rifle is 3.39 J (2.50 ft·lb), compared to 6.44 J (4.75 ft·lb) delivered by the 5.56×45mm NATO in the M16 assault rifle and 7.19 J (5.30 ft·lb) delivered by the 7.62×39mm in the AKM assault rifle.[2]
Military 5.45×39mm ammunition was produced in the former Soviet Union, GDR and Yugoslavia, and is produced in Bulgaria, Poland and Romania. In the former Soviet Union this ammunition is produced in Russia, Kyrgyzstan, Uzbekistan and Ukraine.
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.
Specifications
The 5.45×39mm has 1.75 ml (27 grains H2O cartridge case capacity.
5.45×39mm maximum C.I.P. cartridge dimensions.[3]
Americans would define the shoulder angle at α⁄2 ≈ 20.3°. The common rifling twist rate for this cartridge is 255 mm (1 in 10 inches), 4 grooves, Ø lands = 5.40 mm, Ø grooves = 5.60 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 à Feu Portatives) rulings the 5.45×39mm can handle up to 380.00 MPa (55,114 psi) Pmax 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.This means that 5.45×39mm chambered arms in C.I.P. regulated countries are currently (2014) proof tested at 475.00 MPa (68,893 psi) PE piezo pressure.[3]
Wounding effects
Early ballistics tests done demonstrated a pronounced tumbling effect with high speed cameras.[4] 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. Non-Soviet alarmists feared that this new cartridge had achieved wounding parity with the 5.56x45mm NATO round. To dispute this, 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. [5] 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. [6] 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.
References
- ↑ Assault Rifles and Their Ammunition: History and Prospects by Anthony G. Williams
- ↑ The Russians are coming! The Russians are coming! Or maybe the Polish by Holt Bodinson, Guns Magazine / Sept, 2008
- ↑ 3.0 3.1 C.I.P. TDCC sheet 5,45 x 39
- ↑ Terminal ballistics of the Russian AK 74 assault rifle: Two wounded patients and experimental findings
- ↑ Wounding Potential of the AK-74 Assault Rifle
- ↑ Evolution of the 5,45 mm bullet
