7.62x51mm NATO

The 7.62x51mm NATO is a rifle Cartridge (firearms)|cartridge developed in the 1940's and 50's as a standard for small arms among NATO countries. Specifications for the 7.62x51mm NATO cartridge are not identical to the commercial .308 Winchester though they are safely interchangeable.

The 7.62x51mm NATO 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 FN FAL|FAL became the most popular 7.62mm NATO rifle in Europe and served well into the early 1980s. The M14 was superseded in U.S. service as the infantry adopted the 5.56x45mm NATO|5.56x45mm M16 rifle|M16. However, the M14 and many other firearms that use the 7.62x51 round remain in service, especially in the case of sniper rifles and machine guns. The cartridge is used both by infantry and on mounted and crew-served weapons mounted to vehicles, aircraft and ships.



Overview
The cartridge itself offers similar ballistic performance in most firearms to the .30-06 Springfield that it replaced in U.S. service. Though shorter, standard loadings fire similar bullet weights at similar velocities. Modern propellants allowed the same velocity from a case with less capacity. The smaller case requires less brass and yields a shorter cartridge. This shorter cartridge allows a reduction in the size of the firearms that chamber it.

Development
Work that would eventually develop the 7.62x51mm NATO started just after World War I when it became clear that the powerful .30-06 cartridge was difficult to adapt to Semi-automatic firearm|semi-automatic firearms. 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 appeared to be looming again only a few years later, the .30-06 was the only round available and the M1 Garand rifle|M1 Garand provided U.S. troops with greater firepower than their bolt-action-armed opponents. The Garand performed so well that the U.S. saw little need to replace it during World War II 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 on the Garand. One of the most common complaints was the limited capacity en-bloc clip (ammunition)|clip and many experimental designs modified the weapon with a detachable box Magazine (firearm)|magazine. Springfield Armory's T20, 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 demonstrated power roughly equal to the original .30-06, firing a 147-Grain_(mass)|grain bullet at 2750 ft/s but was approximately .5 inches shorter. The eventual result of this competition was the M14 rifle|T44.



When the U.S. developed the T65, the British took a different route. They had spent considerable time and effort developing the intermediate-power .280 British with an eye towards controllable fully-automatic fire. Meanwhile, the U.S. held to its desire not to reduce the effectiveness of individual shots. The American philosophy was to use automatic fire for emergencies only and continue to use semi-automatic fire the majority of the time. After considerable squabbling the Canadian First Army|Canadian Army announced they would be happy to use the .280 only if the U.S. did as well. 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 rifle|M14 in 1957. Britain and Canada adopted the FN FAL around the same time followed by West German army as the G1. The Germans soon transitioned to a modified version of the Spanish CETME rifle, Heckler & Koch G3. With all three of these firearms, it was clear that the 7.62mm NATO could not be fired controllably in Automatic firearm|fully automatic due to recoil. Both the M14s 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 Barrel (firearms)|barrels.

While all of this was going on, the U.S. Project SALVO concluded that a Burst mode (firearm)|burst of four rounds into a 20 in circle would cause twice the number of casualties as a fully automatic burst by one of these battle rifles &mdash; 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 to prevent the British from using them 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. In addition, the originally issued wooden stocked versions of the M14 were subsceptible to warping from moisture in tropical environments, producing "wandering zeroes" and other accuracy problems (this was fixed with the adoption of fiberglass stocks).

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 NATO ammunition which would allow them a better advantage against a typical People's Army of Vietnam|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.

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 M21 Sniper Weapon System|M21 are still used in the United States military as designated marksman and sniper rifles. Shorter, easier to handle 7.62mm rifles like the Heckler & Koch G3 stayed in service due to their accuracy, range, cartridge effectiveness and reliability. The 7.62x51mm NATO 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 M1919 Browning machine gun|M1919A4 from the WWII era. These have been replaced to a considerable extent in the squad automatic weapon | light machinegun role by .223 weapons, such as the widespread use of the 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 Corp.|Olin Corporation) 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
Image:7.62 NATO tracer rounds, in stripper clip.JPG|thumb|right|7.62mm, NATO, Red-tipped tracer ammunition, M62: 142 gr 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 gr 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 gr 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 gr 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 (SLAP), 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.
 * 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): 144-grain 7.62x51mm NATO ball cartridge. Australian equivalent to U.S. M80 round.  In service with the Australian Defence Force.