7.62×51 NATO

7.62x51 mm NATO
NATO 7.62 x 51 mm rounds are longer and slightly narrower than an LR6 (AA) battery
Type	Rifle
Place of origin	United States
Service history
In service	1954-present
Used by	United States, NATO, others.
Wars	Vietnam War and most conflicts since
Specifications
Parent case	.300 Savage
Case type	Rimless, Bottleneck
Bullet diameter	7.82 mm (0.308 in)
Neck diameter	8.58 mm (0.338 in)
Shoulder diameter	11.35 mm (0.447 in)
Base diameter	11.84 mm (0.466 in)
Rim diameter	11.94 mm (0.47 in)
Rim thickness	1.27 mm (0.05 in)
Case length	51.05 mm (2.01 in)
Overall length	69.85 mm (2.75 in)
Rifling twist	1:12"
Primer type	Large Rifle
Maximum pressure	344.74 MPa (~50000 psi)
Ballistic performance
Bullet weight/type	Velocity	Energy
146.6 gr (9.5g)	2756 ft/s (~840 m/s)	2472 ft·lbf (~3362 J)
Source: Popenker ^[1]

NATO's 7.62x51mm rifle cartridge was adopted in the 1950s as a standard firearm cartridge among NATO countries, though it has also become popular among civilians.

The military 7.62x51mm cartridge is not identical to the commercial .308 Winchester. However, NATO controls specifications for the military round while SAAMI controls specifications for the civilian round. The specifications have been established for two different uses. (1) the SAAMI standard pressure is 50,000 on the (CUP) scale or 62,000 psi, measured with a piezoelectric gauge, for the civilian round. The NATO specification for 7.62x51mm is 50,000 psi.^[2] And (2) headspace; the military chamber is specified to be 1.645 inches, compared to the civilian chamber of 1.632 inches. Though this difference is just 0.013 inches,^[3] a chamber of acceptable military length will put excessive stress on the thinner civilian brass, causing premature head separation. It is not safe to mix .308 Win and 7.62x51mm ammunition, problems can be encountered due to the maxium pressures developed while firing and this is compunded by the different headspace requirements for each.^[4]

The 7.62x51mm cartridge was introduced to military service in rifles and machine guns. It was introduced in U.S. service in the M14 Rifle and M60 Machine gun in the late 1950s. Fabrique Nationale's FAL became the most popular 7.62 NATO rifle in Europe and served into the early 1980s. The M14 was superseded in U.S. service as the infantry adopted a new round with the M16. However, the M14 and many other firearms that use the round remain in service. The round is used by infantry and from ground vehicles, aircraft and ships. It is used in the GE M134 Minigun as well.

Overview

The round itself offers similar ballistic performance in most firearms to the round it replaced in U.S. service, the .30-06 Springfield. While the cartridge itself is shorter, the actual bullet and loadings are about the same (muzzle velocities on the order of 860 m/s (2,800 ft/s) for both). Due to more modern propellants, less volume could be dedicated to holding them in the 7.62x51 cartridge than was needed in the .30-06. The smaller case uses less brass, and firearms that use the round can be smaller, but the reduced size limits flexibility in civilian use, hindering performance with heavier bullets and slower-burning, lower-density powders (see internal ballistics).

Development

The development work that would eventually develop into the 7.62x51mm started just after World War I, when it became clear that the long cartridge of the U.S. standard .30-06 round made it difficult to use in semi- and fully automatic weapons (the .30-06 was in turn derived from an earlier .30-03 cartridge), and had more case capacity than was needed. A "shorter" round would allow the firing mechanism to be made much smaller, and improve the feeding, both of which would allow for higher rates of fire. At the time one of the most promising designs was the .276 Pedersen, but in 1932 it was rejected with an Army recommendation that only rounds of .30 inch (7.62 mm) would meet requirements.

Thus when the war appeared to be looming again only a few years later, the .30-06 was the only round available. Nevertheless the U.S. Army did use it to great effect in the M1 Garand, which provided U.S. troops with considerably higher firepower than most of their bolt-action-armed opponents. The Garand performed so well that the U.S. saw little need to replace it until almost a decade later, and the .30-06 remained in service well beyond the Korean War and into the 1960s.

During the 1940s and early 1950s several experiments were carried out to improve on the Garand. One of the most common complaints was the difficulty in reloading the weapon using its en bloc clips, and many experimental designs modified the weapon with a detachable box magazine. One of these, Springfield Armory's T20, was a fully automatic version. The U.S. Army found that this weapon performed so well that they began to consider replacing the Garand, and decided it was also time to look at improved ammunition once again.

The test program continued for several years, including both the original .30-06 round and a modified .300 Savage (then known as the T65). In the end, the T65 design demonstrated power roughly equal to the original .30-06, firing a 147-grain bullet at 2,750 feet per second, while being somewhat shorter and much more reliable in feeding. The T44, an adaptation of the T20 to fire the new round, was the almost-uncontested winner of the competition.

When the U.S. announced its intentions to introduce the T65, the British were incensed. They had considerable evidence to demonstrate that their own .303 British could not be fired controllably in a shoulder-fired automatic rifle, and the somewhat more powerful T65 would be even harder to control. They had spent considerable time and effort developing an intermediate-power round, the .280, to solve these problems. The U.S. countered with its pre-WWII requirements that stated that only a .30-caliber design would do. After considerable squabbling between the two armed forces, the argument was settled when the Canadian Army announced they would be happy to use the .280, but only if the U.S. did as well — this amounted to a tacit agreement to use the T65, as it was clear the U.S. would not use the .280. The T65 was chosen as the NATO standard in 1954.

The T44 was adopted as the M14 in 1957. Britain and Canada began receiving FN FALs around the same time, as the West German army adopted a modified version of the Spanish CETME rifle, as the Heckler & Koch G3. However it was not long before those involved realized the British had been right all along: the .308 could not be fired accurately in fully automatic due to recoil. M14s were later delivered with the fully automatic selection locked out, and adaptations to the FAL to allow it included the addition of a bipod and heavier barrel.

While all of this was going on, the U.S. Project SALVO concluded that a burst of four rounds into a 20-inch circle would cause twice the number of casualties as a fully automatic burst by one of these battle rifles — regardless of the size of the round. They suggested using a much-smaller .22 caliber cartridge with two bullets per cartridge (a "duplex load"), while other researchers investigated the promising flechette rounds that were even lighter but offered better penetration than even the .30-06. These studies were kept secret in case the British found out about them and used as evidence in favour of their smaller rounds.

When the M14 arrived in Vietnam, it was found to have a few disadvantages. The rifle's length was not well suited for jungle warfare. Also, the weight of 7.62x51mm cartridges limited the total amount of ammunition that could be carried when compared with 7.62x39mm AK-47 ammunition.

Fighting between the big-round and small-round groups reached a peak in the early 1960s, when test after test showed the .223 Remington round fired from the AR15 allowed an 8-soldier unit to outgun an 11-soldier unit armed with M14s. U.S. troops were able to carry more 5.56x45mm ammunition which would allow them a better advantage against a typical NVA unit armed with AK-47s. In 1964, the U.S. Army started replacing their M14s with the M16, incurring another series of complaints from the British. However a large number of troops preferred the M14 because of its more powerful cartridge and because it was more durable than the new M16.^{[citation needed]}

Regardless of the M14 having disadvantages in jungle warfare, 7.62x51mm rifles stayed in military service around the world due to several factors. The 7.62x51mm has proved much more effective than 5.56x45mm at long ranges, and has since found popularity as a sniping round. For instance, M14 variants such as the M21 are still used in the United States military as designated marksman and sniper rifles. Shorter, more maneuverable 7.62mm rifles like the Heckler & Koch G3 stayed in service due to their accuracy, range, power, and reliability.

The 7.62x51mm round nevertheless met the designer's demands for fully automatic reliability with a full-power round. It remained the main machine gun round for almost all NATO forces well into the 1990s, even being used in adapted versions of older .30-06 machine guns such as the Browning M1919A4 from the WWII era. These too have been replaced to some extent by .223 weapons, such as the widespread FN Minimi, but they remain the primary armament on most flexible mountings such as helicopters, jeeps, and tanks.

Winchester Ammunition (a division of the Olin Corporation, a major supplier of ammunition to the U.S. military) saw the market for a civilian model of the T65 cartridge and released it commercially in 1952 as the .308 Winchester, two years prior to adoption of the cartridge by NATO.

Military Cartridge Types

Cartridge, Grenade, L1A1 (United Kingdom): 7.62x51mm grenade launching cartridge with one subvariant (L1A2) with unknown differences.
Cartridge, Ball, L2A1 (United Kingdom): 7.62x51mm ball cartridge, with three subvariants (A2-A4) with unknown differences.
Cartridge, Tracer, L5A1 (United Kingdom): 7.62x51mm tracer cartridge, designed to last out to 1000 meters. Four subvariants exist, with brighter ignition (A2), tracer reduced to 750 meters (A3), with a pistol powder charge (A4), and with improved ballistics (A5).
Cartridge, Caliber 7.62mm, NATO, Ball, F4 (Australia): 146-grain 7.62x51mm NATO ball cartridge. Australian equivalent to U.S. M80 round. In service with the Australian Defence Force.

7.62mm, NATO, Tracer, M62: 142-grain tracer cartridge.

Cartridge, Caliber 7.62mm, NATO, Ball, M59 (United States): 150.5-grain 7.62x51mm NATO ball cartridge. A further development of the initial T65 cartridge.
Cartridge, Caliber 7.62mm, NATO, Armor Piercing, M61 (United States): 150.5-grain 7.62x51mm NATO armor piercing round, black cartridge tip.
Cartridge, Caliber 7.62mm, NATO, Tracer, M62 (United States): 142-grain tracer cartridge, orange cartridge tip.
Cartridge, Caliber 7.62mm, NATO, Grenade, M64 (United States): 7.62x51mm NATO grenade launching blank.
Cartridge, Caliber 7.62mm, NATO, Ball, M80 (United States): 146-grain 7.62x51mm NATO ball cartridge.
Cartridge, Caliber 7.62mm, NATO, Match, M118 (United States): 173-grain 7.62x51mm NATO Full Metal Jacket Boat Tail round specifically designed for Match purposes. Introduced in 1968 as XM118, standardized in 1970 as M118. Produced at Lake City Army Ammunition Plant.
Cartridge, Caliber 7.62mm, NATO, Ball, Special, M118 (United States): 173-grain 7.62x51mm NATO Full Metal Jacket Boat Tail round specifically designed for match purposes. Produced by Lake City Army Ammunition Plant. This is an interim match round which utilized M80 ball brass with the 173-grain FMJBT bullet. During this period in the early to late 1980s the performance of the round declined. Powder, primer, brass, bullets were no longer produced in matching lots.
Cartridge, Caliber 7.62mm, NATO, Ball, Special, M118LR (United States): 175-grain 7.62x51mm NATO Hollow Point Boat Tail round specifically designed for long-range sniping. Produced at Lake City Army Ammunition Plant.
Cartridge, Caliber 7.62mm, NATO, Duplex, M198 (United States): 7.62x51mm NATO duplex round with two 84-grain bullets. The developmental designation was T314E3.
Cartridge, Caliber 7.62mm, NATO, Tracer, M276 (United States): 7.62x51mm NATO so-called "Dim Tracer" with reduced effect primarily for use with night vision devices, green cartridge tip with pink ring.
Cartridge, Caliber 7.62mm, NATO, Match, M852 (United States): 168-grain 7.62x51mm NATO Hollow-Point Boat-Tail cartridge, specifically designed for use in National Match competitions, later approved by US Army JAG for combat use by snipers.
Cartridge, Caliber 7.62mm, NATO, Saboted Light Armor Penetrator, M948 (United States): 7.62x51mm NATO Saboted Light Armor Penetrator cartridge.
Cartridge, Caliber 7.62mm, NATO, Armor Piercing, M993 (United States): 126.6-grain 7.62x51mm NATO armor piercing round, black cartridge tip.

Firearms using the 7.62x51mm NATO round

References

^ Max R. Popenker
^ Accurate Smokeless Powders Loading Guide Number Two (Revised), Book by Accurate Arms Co, Wolfe Publishing, 2000
^ 7.62x51 vs .308 Winchester
^ Tempest in a Cartridge Case - No, Virginia, .308 Win. and 7.62mm NATO Are Not Identical

External links

Various photos of 7.62x51 NATO ammunition

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7.62×51 NATO

Overview

Development

Military Cartridge Types

Firearms using the 7.62x51mm NATO round

Bolt-action

Selective fire, battle rifles, and derivatives

Machine guns

Other

See also

References

External links

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