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300px-NATO 7.62x51

7.62x51mm NATO round compared to AA battery.

The 7.62x51mm NATO (official NATO nomenclature 7.62 NATO) is a rifle cartridge developed in the 1950s as a standard for small arms among NATO countries (not to be confused with the similarly named Russian 7.62x54mmR cartridge).

It was introduced in U.S. service in the M14 Rifle and M60 machine gun in the late 1950s. The M14 was superceded in U.S. service as the infantry adopted the 5.56x45mm NATO M16. However, the M14 and many other firearms that use the 7.62x1 round remain in service, especially in the case of sniper rifles, machine guns, and as the service weapon chosen by special operations forecs. The cartridge is used both by infantry and on mounted and crew-served weapons mounted to vehicles, aircraft, and ships.

Although not identical, the 7.62x51mm NATO and the commercial .308 Winchester cartridges are similar, and even though the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) considers it safe (by not listing it) to fire the NATO round in weapons chambered for the commercial round in weapons chambered for the commercial round, there is a significant discussion about compatible chamber and muzzle pressures between the two cartridges based on powder loads and wall thicknesses on the military vs. commercial rounds.


OverviewEdit

The cartridge itself offered similar ballistic performance in most firearms to the .30-06 Springfield that it replaced in U.S. service. Though shorter, standard loadings for similar bullet weights with only a slight reduction in velocity. Modern propellants allowed for similar performance from a case with less capacity. The smaller case requires less brass and yields a shorter cartridge. This shorter cartridge allows a slight reduction in the size and weight of firearms that chamber it, and somewhat better cycling in automatic and semi-automatic rifles.

DevelopmentEdit

Work that would eventually develop the 7.62x51mm NATO started just after WWI when the large, powerful .30-06 cartridge proved difficult to adapt to semi-automatic rifles. A less-powerful cartridge would allow a lighter firing mechanism. At the time, the most promising design was the .276 Pedersen. When it was eventually demonstrated that the .30-06 was suitable for semi-automatic rifles, the .276 was dropped.

Thus, when war appeard to be looming again only a few years later, the .30-06 was the only round available and the M1 Garand provided US troops with greater firepower than their bolt-action armed opponents. The Garand performed so well that the US saw little need to replace it during WWII and the .30-06 served well beyond the Korean War and into the 1960s.

During the 1940s and early 1950s several experiments were carried out to improve the Garand. One of the most common complaints was the limited capacity en-bloc clip and many experimental designs modified the weapon with a detachable box magazine. Springfield Armory's T20 rifle was a fully automatic version. Though not adopted, experience with a fully automatic Garand laid the groundwork for its replacement.

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 cartridge demonstrated power roughly equal to the original .30-06, firing, a 147-grain bullet at 2,750 fps but was approximately half an inch shorter. The eventual result of this competition was the T44 rifle. The T44 was adopted as the M14 in 1957. Britain and Canada adopted the Belgian FN FAL around the same time followed by the West German Army as the G1. The Germans soon transitioned to a modified version of the Spanish CETME, the Heckler & Koch G3. With all three of these firearms, it was clear that the 7.62 NATO could not be fired controllably in full automatic due to recoil. Both the M14 and FAL would later go through several variations intended to either limit fully automatic selection through semi-auto version or selector locks or improve control with bipods and/or heavier barrels.

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 casue 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 the other researchers investigated the promising flechette rounds that were even lighter but offered better penetration than even the .30-06.

When the M14 arrived in Vietnam, it was found to have a few disadvantages. The rifle's overall 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 the common 7.62x39mm cartridge of the Type 56 and AK-47 assault rifles, which the Vietcong and North Vietnamese were equipped with. In addition, the originally issued wooden stocked versions of the M14 were susceptible to warping from moisture in tropical environments, producing "wandering zeroes" and other accuracy problems (this was fixed with the adoption of fiberglass stocks).

220px-Rifle cartridge comparison

.50 BMG, .300 WIN MAG, .308 WIN (7.62 NATO), 7.62×39mm, 5.56 NATO, and .22 LR.

Fighting between the big-round and small-round groups reached a peak in the early 1960s, when test after showed .223 Remington cartridge fired from the AR-15 allowed an 8-soldier unit to outgun an 11-soldier unit armed with M14s. U.S. troops were able to carry more than twice as much 5.56x45mm ammunition as 7.62x51mm for the same weight, which would allow them a better advantage against a typical NVA unit armed with Type 56-1s.

Rifle Cartridge Cartridge Weight Weight of loaded magazine 10 Kg ammo load
M14 7.62x51mm 393 gr (25.4g) 20 rds @ .68 kg 14 mags / 280 rds
M16 5.56x45mm 183 gr (11.8g) 20 rds @ .3 kg 33 mags / 660 rds
AK47 7.62x39mm 281 gr (18.2g) 30 rds @ 1.2 kg* 8 mags / 240 rds

(*AK-47 magazines are much heavier tha M14 and M16 magazines)

In 1964, the U.S. Army started replacing their M14s with the M16, incurring another series of complaints from the British. Regardless of the M14 having disadvantages in jungle warfare, 7.62x51mm NATO rifles stayed in military service around the world due to several factors. The 7.62x51mm NATO 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 Mk 14 Mod 0 Enhanced Battle Rifle and M21 are still used in the United States military as designated marksman and sniper rifles. Shorter, easier to handle 7.62x51mm NATO rifles like the Heckler & Koch G3 stayed in service due to their accuracy, range, cartridge effectiveness and reliability.

220px-7,62mm G3 oder MG3

Three recovered 7.62x51mm NATObullets (next to an unfired cartridge), showing rifling marks.

The 7.62x51mm NATO round nevertheless met the designer's demands for fully automatic reliabiltiy 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 have been replaced to a considerable extent in the light machinegun role by 5.56x45mm NATO weapons, such as the widespread use fo the M249 SAW, but the 7.62mm round is still the standard chambering for most general-purpose machine guns such as the M60E4, the M240 and the German HK21, and the flexible mountings such as helicopters, jeeps, and tanks.

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

Military cartridge typesEdit

220px-Cartridges comparison

Comparison of 7.62 mm NATO, 5.56 mm NATO and 9 mm NATO.

  • Cartridge, Caliber 7.62mm, NATO, Ball, M59 (United States): 150.5-grain 7.62x51m NATO ball cartridge. A further development of the initial T65 cartridge.
  • Cartridge, Caliber 7.62mm, NATO, High Pressure Test, M60 (United States): 7.62x51mm NATO test cartridge. The cartridge is not for field use, but is used for proof firing of weapons during manufacture, test, or repair. The cartridge is identified by a stannic-stained (silvered) cartridge tip.
  • 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.
  • 220px-7.62x51 5.56x45

    The 7.62x51mm NATO and the 5.56x45mm NATO cartridges compared to a AA battery.

    Cartridge, Caliber 7.62mm, NATO, dummy, M63 (United States): The cartridge is used for practice in loading 7.62mm weapons for simulated firing to detect flinching of personnel during firing and for inspecting and testing the weapon mechanism. The cartridge is identified by six longitudinal corrugations (flutings0 on the cartridge case. There is no primer and no vent hole in the primer pocket.
  • Cartridge, Caliber 7.62mm, NATO, Grenade, M64 (United States): 7.62x51mm NATO grenade launching blank. The cartridge is identified by a rose-petal closure of the cartridge case mouth and sealed with red lacquer. The cartridge provides pressure upon functioning to project rifle grenades to a desired target when using a grenade projectile adapter and dragon missile launch effect trainer.
  • Cartridge, Caliber 7.62mm, NATO, Ball, M80 (United States): 147-grain, 7.62x51mm NATO ball cartridge.
  • Cartridge, Caliber 7.62mm, NATO, Blank, M82 (United States): 7.62x51mm NATO cartridge is used in rifles and machineguns equipped with blank firing attachments to simulate firing in trainign excersises and for saluting purposes. The cartridge is identified by its double tapered neck and absence of a bullet.
  • Cartridge, Caliber 7.62mm, NATO, Ball, Silent, XM115 (United States): Little is known of this round, but it was some attempt to quiet the round. Never adopted.
  • Cartridge, Caliber 7.62mm, NATO, Ball, Special, M118 (United States): 173-grain 7.62x51mm Full Metal Jacket Boat Tail round specifically designed for match purposes. Produced by Lake City Amry Ammunition Plant. This is an interim match round which utilized M80 ball brass with the 173-grain FMJBT bullet.
  • Cartridge, Caliber 7.62mm, NATO, Ball, Special, M188LR (United States): 175-grain 7.62x51mm NATO Hollow Point Boat Tail round specifically designed for long-range sniping.

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