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 FAL became the most popular 7.62 mm 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 The M14 was superseded in U.S. service as the infantry adopted the 5.56x45mm M16.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 round is used by infantry and from ground vehicles, aircraft and ships.
While similar in appearance, the military 7.62x51 NATO cartridge is not identical to the commercial .308 Winchester. However, their interchange is not listed as unsafe in either combination.
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 , while being somewhat shorter and much more reliable in feeding. The T44, an adaptation of the T20 to fire the new round, was eventually (and narrowly) selected after a protracted competition characterized by inconsistent funding and unclear (and sometimes contradictory) requirements for a new service rifle.
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 British, to solve these problems. The U.S. countered with its pre-WWII requirements that stated that only a .30-caliber design would do, ignoring the fact that said requirement was based on lack of funding rather than any attempt to field an ideal service rifle cartridge. After considerable squabbling between the United States on one hand and the UK, Canada, and Belgium on the other, 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, or earlier (due to problems with M14 production rates), as the West German army first adopted the FN FAL as the G1, and then replaced it with a modified version of the Spanish CETME rifle, as the Heckler & Koch G3, as Belgium would not grant a production license to the West German government. 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 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. 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- 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 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 are still used in the United States military as designated marksman and sniper rifles. Shorter, easier to handle 7.62 mm 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 M1919A4 from the WWII era. These too have been replaced to some extent 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 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.
Commonly confused, the M852 and M118LR are NOT "hollow point" rounds. Instead, they are classified as "open tip". The open tip design is used to reduce drag, whereas a hollow point design is used to increase fragmentation upon entry into a target.