7.62×39mm

The 7.62×39mm (aka 7.62 Soviet, formerly .30 Russian Short) round is a rimless bottlenecked intermediate cartridge of Soviet origin. The cartridge is widely used due to the worldwide proliferation of Russian SKS and AK-47 pattern rifles, as well as RPD and RPK light machine guns.

The AK-47 was designed shortly after WWII, later becoming the AKM because the production of sheet metal had issues when first initiated. This weapon is now the world's most widespread military-pattern rifle. The cartridge remained the Soviet standard until the 1970s. It was partly replaced in Soviet service by the 5.45×39mm cartridge, which was introduced with the new AK-74 rifle, and continues in service with the modernized current-issue Russian Armed Forces AK-74M service rifle, as well as the AK-12 rifle. In the 21st century the 7.62×39mm remains a common service rifle chambering, including for newly developed rifles like the AK-15.

History

On July 15, 1943, the Technical Council of the People's Commissariat for Armaments (russian: Техсовет Наркомата Вооружения) met to discuss the introduction of a Soviet intermediate cartridge. The Soviet planners also decided at this meeting that their new cartridge was to be used in a whole range of infantry weapons, including a semi-automatic carbine, a selective fire rifle, and a light machine gun. The job of designing the Soviet intermediate cartridge was assigned to a committee led by chief designer N.M. Elizarov (), assisted by P.V. Ryazanov (), B.V. Semin (), and I.T. Melnikov (). Elizarov collaborated closely with some leading weapons designers, including Fedorov, Tokarev, Simonov, and Shpagin. About 314 cartridge designs were considered theoretically, before narrowing the selection down to eight models that were physically constructed and tested. Most of the development work on the new cartridge took place at OKB-44, which was soon thereafter renamed as NII-44, and which in 1949 was merged with NII-61, itself merged with TsNIITochmash in 1966.

A first variant of the new cartridge was officially adopted for service after completing range trials in December 1943; it was given the GRAU index 57-N-231. This cartridge actually had a case length of 41 mm, so it is sometimes referred to as the 7.62×41. The bullet it contained was 22.8 mm long and had a core made entirely of lead. This bullet has a somewhat stubbier appearance than later 7.62×39 bullets, with its maximal radius being attained after only 13.01 mm from its tip, and it was lacking a boat tail. After some further refinements, a pilot production series of this cartridge began in March 1944."Патрон – основа оружия. Глава третья. Из истории автоматного 7,62-мм патрона образца 1943 г. (7,62х39)", ''Оружие'' 2005/9, pp. 21–44

After more detailed testing results became available, starting in 1947 the cartridge was tweaked by the Ulyanovsk Machine Building Plant to improve its accuracy and penetration. Initially, the boat tail had been omitted because the Soviet designers had assumed (incorrectly) that it would only make a difference at long ranges, when the bullet became subsonic, and the accuracy of the intermediate cartridge at these ranges was considered inconsequential. However, further testing showed that the boat tail improved accuracy even at shorter ranges, where the bullet was still supersonic. In order to maintain the overall mass of the bullet, after adding the boat tail, the ogival head section of the bullet was lengthened as well, making the bullet more streamlined overall. The maximum radius was now attained at some 15.95 mm from the tip and the overall length of the bullet increased to 26.8 mm. In order to preserve the total length of the cartridge, the case sleeve was shortened to 38.7 mm (and by rounding it is customarily referred to as 7.62×39.) Additionally, the new bullet had a core made of lead wrapped in low-carbon steel . The use of low-carbon (mild) steel was guided mostly by the desire to reuse some industrial equipment that was manufacturing the 7.62×25mm Tokarev cartridge rather than by bullet fragmentation considerations. This bullet was given the acronym "7.62 PS" (76.2 ПС). The "S" initially stood for "surrogate" (, '), but later the letter was taken to refer to the steel component (, ') of the core, which accounted for about 50% of the core volume. The 7.62×39 cartridge equipped with the PS bullet finally overcame all objections of the GAU in mid-1947, when it was ordered into series production and given the index 57-N-231S. Field tests of the round and the new prototype AK-47 were carried out at the NIPSVO from December 16, 1947, to January 11, 1948.

The design that was ultimately selected by the Soviets has more dimensional similarities to the GECO cartridge used in the Vollmer M35 than with the Polte round used by the later German Sturmgewehr. Some authors, including C. J. Chivers, have speculated that the Soviets may have had access to the works of GECO and Vollmer during 1940, when Hitler allowed a large number of Soviet engineers to tour various German armament factories. Anthony G. Williams, however, argues that the Soviet M43 round was so different that it was possible to dismiss the idea that it was a copy of any German round in existence at the time.

The 57-N-231S cartridge used a "bimetallic" (steel and copper) case. In the early 1960s, a "lacquered" steel case was introduced, and the new cartridge was initially given the designation 57-N-231SL. In an effort to simplify terminology, sometime thereafter the 57-N-231 designation was recycled to denote all steel-core 7.62×39 Soviet ammunition, irrespective of case build.

In the mid 1950s, Elizarov's team, now working at NII-61, developed a special subsonic bullet for the 7.62×39 cartridge. It was adopted for service in 1962, and given the army designation "7.62 US" (''US'' stood for , meaning "reduced speed") and the GRAU index 57-N-231U. The subsonic bullet was considerably longer (33.62 mm) and heavier (12.5 g) than the PS bullet, and also had a different, non-layered core structure. The core of its head section was entirely made of tool steel, followed by another section entirely made of lead. The subsonic bullet also has a larger maximum diameter of 7.94 mm compared to all other 7.62×39 bullets that peak at 7.91 mm diameter; the larger diameter of the lead-core section was intended to provide a tighter fit to the barrel by better engaging the rifling grooves. The 7.62 subsonic ammo was intended to be fired from AK-47-type rifles equipped with the PBS-1 silencer, and developed a muzzle velocity of about 285–300 m/s. For recognition, this ammo typically has the bullet tips painted black with green band underneath.

After 1989, the regular (PS) Russian bullets started to be manufactured with a steel core with a higher carbon concentration and subjected to heat treatment. This change improved their penetration by 1.5–2 times. It is not possible to externally distinguish these bullets from the earlier, softer PS ones except by year of fabrication. At about the same time, tool steel was adopted for a normal velocity 7.62×39 bullet. Called BP, this bullet was developed in the 1980s and 1990s. It was officially adopted for Russian service in 2002 under the service name "7.62 BP", and with the GRAU designation 7N23. The BP bullet is claimed to achieve over three times the penetration of the PS bullet; it can defeat the Russian bullet-proof vest with designation 6B5 at distances below 250 meters. The BP cartridge has the tip of its bullet painted black. The BP bullet itself is slightly longer (27.4 mm) compared to the PS bullet, but has the same mass of 7.9 grams.

At the same 1943 meeting that decided the development new cartridge, the Soviet planners decided that a whole range of new small arms should use it, including a semi-automatic carbine, a fully automatic rifle, and a light machine gun. Design contests for these new weapons began in earnest in 1944.

Variants

M43

The original Soviet M43 bullets are 123 grain boat-tail bullets with a copper-plated steel jacket, a large steel core, and some lead between the core and the jacket. The cartridge itself consisted of a Berdan-primed, highly tapered (usually steel) case which seats the bullet and contains the powder charge. The taper makes it very easy to feed and extract the round, since there is little contact with the chamber walls until the round is fully seated. This taper is what causes the AK-47 to have distinctively curved magazines (helping to distinguish AK-47s from AK-74s, which feed from a much straighter magazine). While the bullet design has gone through a few redesigns, the cartridge itself remains largely unchanged. The ballistic coefficient (G7 BC) of the M1943 pattern full metal jacket boat bullet is 0.138.

The complete solidity of the M43 projectile causes its only drawback—it is very stable, even while traversing tissue. It begins to yaw only after traversing nearly of tissue.Military rifle bullet wound patterns – by Martin L. Fackler. From: http://www.uthr.org/SpecialReports/Military_rifle_bullet_wound_patterns.htm . Retrieved on November 9, 2011 This greatly reduces the potential wounding effectiveness of the projectile.

Type 56: Chinese mild steel core

Chinese (Type 56) military ammunition (developed in 1956) is an M43-style cartridge with a mild steel core (MSC) and a copper-plated steel jacket.
In 1956, the Chinese developed their own 7.62x39mm assault rifle, also designated Type 56. It is a variant of the Soviet-designed AK-47 (specifically Type 3 and AKM) assault rifles. Production started in 1956 at State Factory 66 but was eventually handed over to Norinco, who continues to manufacture the rifle, primarily for export. Norinco developed and produced 7.62x39mm ammunition for the Type 56 rifle. The Chinese ammunition (as well as all other M43 ammunition) is currently banned from importation in the United States because U.S. federal law classifies the round as an armor-piercing handgun round. This classification is based on materials and bullet design rather than on empirical ability to penetrate armor.

"7.62×38mm" Dutch

In the late 1950s West Germany was investigating the concept of an intermediate service cartridge (''Mittelpatrone''). As part of a ballistic study, the West German government commissioned reverse-engineered copies of the 7.62mm M43 round to be made for use in SKS rifles and RPD light machine guns that they had obtained. The Dutch firm NWM (''Nederlandsche Wapen-en Munitiefabriek'') was contracted in 1958 to make the ammunition. Specifications based on captured samples were drawn up in April, 1958 and production began in 1959.

There were two different cartridges commissioned. The first was a lead-core bullet (''Weichkern'', or "soft core") with a gilding-metal jacket. It had a plain tip to indicate that it was standard Ball ammunition. The other was an Armor-Piercing bullet with a sintered iron or steel core and a gilding-metal jacket. It had a tip painted with black enamel (as per NATO standards) to indicate it was Armor Piercing. The brass cases were required to have a length between 38.3- and 38.7 mm, so the cartridge was designated the "7.62×38mm". The headstamp bore the metric designation (7.62×38mm) at 12 o'clock, the 2-digit year at 4 o'clock, and the contractor (NWM) at 8 o'clock.

M67

In the 1960s Yugoslavia experimented with new bullet designs to produce a round with a superior wounding profile, speed, and accuracy to the M43. The M67 projectile is shorter and flatter-based than the M43. This is mainly due to the removal of the mild steel insert. This has the side effect of shifting the center of gravity rearward in comparison to the M43. This allows the projectile to destabilize nearly earlier in tissue. This causes a pair of large stretch cavities at a depth likely to cause effective wound trauma. When the temporary stretch cavity intersects with the skin at the exit area, a larger exit wound will result, which takes longer to heal. Additionally, when the stretch cavity intersects a stiff organ like the liver, it will cause damage to that organ. However, the wounding potential of M67 is mostly limited to the small permanent wound channel the bullet itself makes, especially when the bullet doesn't yaw (tumble).

Commercial ammunition

Commercial Russian-made 7.62×39mm ammunition, such as those sold under the Wolf Ammunition brand name, are also available in full metal jacket (FMJ), soft-point (SP) and hollow-point (HP) variety. The SP bullets offer improved expansion. Commercial ammunition differs from most military ammunition in regards to bullet composition, specifically heavy use of lead instead of soft steel or tool steel.

Cartridge dimensions

The 7.62×39mm has 2.31 ml (35.6 grain H₂O) cartridge case capacity.

7.62×39mm maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm).

Americans define the shoulder angle at alpha/2 ≈ 16.4 degrees. The common rifling twist rate for this cartridge is 240 mm (1 in 9.45 in), 4 grooves, Ø lands = , Ø grooves = , land width = and the primer type is usually large rifle, with the exception of commercial Remington/UMC brass using small rifle primers.

According to the official C.I.P. (french: Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings the 7.62×39mm can handle up to P_max 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 7.62×39mm chambered arms in C.I.P. regulated countries are currently (2015) proof tested at PE piezo pressure.

The SAAMI maximum average pressure (MAP) for this cartridge is piezo pressure.

Basic specifications of 21st century Russian service loads

The 7.62×39mm rounds in use with the Armed Forces of the Russian Federation are designed for AKM assault rifles and AK-derived light machine guns. As per 2003 there were several variants of 7.62×39mm produced for various purposes. All use clad metal as case material.

The ''57-N-231'' conventional steel-core bullet is designed to engage personnel and weapon systems. The bullet has a steel core and has a ballistic coefficient (G1 BC) of approximately 0.304 and (G7 BC) of approximately 0.152. The tip has no distinguishing colour. It can penetrate a thick St3 steel plate at and 6Zh85T body armour at .

The ''7N23'' armour-piercing bullet, introduced in 2002, has a 3.6 g (55.6 gr) sharp-pointed steel penetrator made of steel U12A and retains the soft lead plug in the nose for jacket discarding. The bullet has a black tip.

The ''57-N-231P'' is a tracer round designed for fire adjustment and target designation. The bullet has a green tip and the tracer burns for . The ''57-T-231PM1'' is an improved tracer round which initiates at from the muzzle and burns for .

R₅₀ at means the closest 50 percent of the shot group will all be within a circle of the mentioned diameter at .

Military 7.62×39mm ammunition is purportedly tested to function well in temperatures ranging from cementing its usefulness in cold polar or hot desert conditions.

Hunting and sport use

Since approximately 1990, the 7.62×39mm cartridge has seen some use in hunting arms in the U.S. for hunting game up to the size of whitetail deer, as it is slightly less powerful than the .30-30 Winchester

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