The 7.62×51mm NATO (official NATO nomenclature 7.62 NATO) is a rimless, bottlenecked, centerfire rifle cartridge. It is a standard for small arms among members of the North Atlantic Treaty Organisation (NATO).
First developed in the 1940s, the cartridge was introduced in U.S. service in 1954 for the M14 rifle and M60 machine gun.
The later adoption of the 5.56×45mm NATO intermediate cartridge and assault rifles as standard infantry weapon systems by NATO militaries started a trend to phase out the 7.62×51mm NATO in that role. Many other firearms that use the 7.62×51mm NATO fully powered cartridge remain in service today, especially various designated marksman rifles/sniper rifles and medium machine guns/general-purpose machine guns (e.g. M24 Sniper Rifle and M240 Medium Machine Gun). The cartridge is also used on mounted and crew-served weapons mounted on vehicles, aircraft, and ships.
Development
Work that would eventually develop the 7.62×51mm NATO started just after World War I when the large, powerful .30-06 Springfield 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 Springfield was suitable for semi-automatic rifles, the .276 Pedersen was dropped.
Thus, when war appeared to be looming again, only a couple of decades later, the .30-06 Springfield was the only round available, and the 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 Springfield served well beyond the Korean War and into the mid-1950s. The .30-06 Springfield was officially replaced by the 7.62 NATO M14 in 1957.
During the 1940s and early 1950s, several experiments were carried out to improve the M1 Garand semi-automatic rifle. One of the most common complaints was the limited-capacity eight-round en-bloc clip, and many experimental designs modified the weapon to use 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 Springfield round and experimental cartridges.
T65 series experimental cartridges During the 1940s, the .300 Savage became the basis for experiments on behalf of the U.S. Military that resulted in the development of the T65 series of experimental cartridges. The original experimental case design by the Frankford Arsenal was designated the T65 and was similar to the .300 Savage case, but with less taper. The experimental cases were made from standard .30-06 Springfield cases, which had slightly less capacity than standard .300 Savage cases because the Frankford Arsenal cases had slightly thicker case walls. The later T65 iterations were made from shortened .30-06 Springfield cases and were longer compared to the original T65 case, as the .300 Savage has a shorter case length than the resulting 7.62 NATO. The resulting cartridges provided a ballistic performance roughly equal to the U.S. military .30-06 Springfield 1906 pattern M1906 and 1938 pattern M2 service cartridges. Over forty years of technical progress in the field of propellants allowed for similar service cartridge performance – firing a bullet at with muzzle energy – from a significantly shorter, smaller case with less case capacity. The eventual result of this competition was the T44 rifle.
DesignationCaseDescriptionManufacturerMetric T65 T65 case (47 mm) Steel jacket lead core flat base bullet Frankford Arsenal 7.62×47mm T65E1 FAT1 case (49 mm) Steel jacket lead core Frankford Arsenal 7.62×49mm T65E2 FAT1E1 (49 mm – 30° shoulder) Steel jacket lead core Frankford Arsenal 7.62×49mm T65E3 FAT1E3 (51 mm – 20° shoulder) Steel jacket lead core Frankford Arsenal 7.62×51mm T65E4 FAT1E3 (51 mm – 20° shoulder) Steel jacket lead core boat-tail bullet with a No. 10 ogive point Frankford Arsenal 7.62×51mm T65E5 FAT1E3 (51 mm – 20° shoulder) Steel jacket lead core boat-tail bullet Frankford Arsenal 7.62×51mm
When the United States developed the T65 cartridge, the British military took a different route. They had spent considerable time and effort developing the intermediate-power .280 British (7 mm) cartridge with an eye towards controllable fully automatic fire. The U.S. held to its desire not to reduce the effectiveness of individual aimed shots. The American philosophy was to use automatic fire only in emergencies and continue to use semi-automatic fire for the majority of the time. After considerable debate, the Canadian Army announced they would be happy to use the .280 but only if the U.S. did as well. It was clear the U.S. was not going to use the .280 British. The British did start introducing the .280 British along with the bull-pup Rifle No. 9, but the process was stopped in the interests of harmonization across NATO. The T65E5 (7.62×51mm) was chosen as NATO's standard cartridge in 1954.
Winchester saw a market for a civilian model of the late T65 series designs and introduced it in 1952, two years before NATO adopted the T65E5 experimental cartridge iteration as 7.62×51mm NATO in 1954. Winchester branded the cartridge and introduced it to the commercial hunting market as the .308 Winchester. The dimensions of .308 Winchester are almost the same as those of 7.62×51mm NATO. The chamber of the former has a marginally shorter headspace and thinner case walls than the latter, due to changes in specifications between 1952 and 1954. This allows 7.62×51mm NATO ammunition to feed reliably in rifles chambered for .308 Winchester, but can cause .308 Winchester ammunition cases to rupture when fired in rifles chambered for 7.62×51mm NATO.
Adoption in battle rifles
The T44 rifle was adopted as the M14 rifle in 1957. Around the same time, Britain and Canada adopted the Belgian FN FAL (L1A1 SLR British) as the L1, followed by the West German army designated as the G1. The Germans soon transitioned to a modified version of the Spanish CETME rifle by Heckler & Koch that was adopted as the G3. With all of these firearms, it was clear that the 7.62×51mm NATO could not be fired controllably in fully automatic because of recoil. Both the M14 and FAL were later modified to limit fully automatic fire by introducing semi-automatic versions or selector locks. Efforts were also made to improve control with bipods or heavier barrels.
While 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 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). At the same time, other researchers investigated the promising flechette rounds that were 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 7.62×51mm NATO cartridges limited the total amount of ammunition that could be carried in comparison with the 7.62×39mm cartridge of the Type 56 and AK-47 rifles, with which the Vietcong and North Vietnamese Army soldiers were equipped.
Fighting between the big-round and small-round groups reached a peak in the early 1960s, when test after test showed the .223 Remington (M193 5.56×45mm) cartridge fired from the AR-15 allowed an eight-soldier unit to outgun an 11-soldier unit armed with M14s at ranges closer than . U.S. troops were able to carry more than twice as much 5.56×45mm ammunition as 7.62×51mm NATO for the same weight, which allowed them an advantage against a typical NVA unit armed with Type 56-1s.
RifleCartridgeCartridge weightWeight of loaded magazineMax. 10 kilogram ammo load M14 (1959) 7.62×51mm NATO 20 rd magazine at 13 magazines at for 260 rounds M16 (1962) .223 Remington (M193 5.56×45mm) 20 rd magazine at 31 magazines at for 620 rounds AK-47 (1949) 7.62×39mm 30 rd magazine at 12 magazines at for 360 rounds
In 1964, the U.S. Army began replacing its M14s with M16s, causing further compatibility issues. Regardless of the M14 having disadvantages in jungle warfare, 7.62×51mm NATO rifles stayed in military service around the world due to several factors. The 7.62×51mm NATO has proved much more effective than 5.56×45mm NATO at long ranges, and has since found popularity as a sniping round. For instance, the Mk 14 Enhanced Battle Rifle, an M14 variant, and the M25 sniper rifle were utilized in the United States military as designated marksman and sniper rifles, respectively. Shorter, easier-to-handle 7.62mm rifles like the G3 stayed in service due to their accuracy, range, cartridge effectiveness, and reliability. In addition, continued if limited use in infantry rifles is a logistical convenience, given the preference for 7.62×51mm NATO across NATO for general-purpose machine guns.
Specialized use
Sniper and designated marksman rifles
Specialized loadings were created for 7.62×51mm NATO-chambered sniper rifles. They used heavier and more aerodynamic bullets that had a higher ballistic coefficient than standard ball rounds, meaning they shed velocity at longer ranges more gradually. Maintaining velocity is important for accurate long-range shots because dropping from supersonic to transonic speeds disturbs the flight of the bullet and adversely affects accuracy. The standard M80 ball round weighs 147 gr and, from an M14 rifle and M60 machine gun, has a muzzle velocity faster than the M118LR 175 gr sniping round. However, the M80 drops to subsonic velocity around , while the initially slower M118LR is supersonic out to due to its low-drag bullet.
The 7.62×51mm NATO round remains in use in designated marksman rifles such as the Heckler & Koch HK417, SIG 716, FN SCAR, L129A1, Colt Canada C20 DMR and LMT MARS-H based riles to take advantage of the effective range and accuracy potential compared with intermediate rifle rounds. Designated marksman rifles have to be effective, in terms of hit rates and terminal ballistics, at application ranges exceeding those of ordinary assault rifles and battle rifles, but do not require the extended-range performance of a dedicated sniper rifle. Depending on the military, specialized 7.62×51mm NATO ammunition is sometimes issued to the designated marksman.
General-purpose machine guns
The 7.62×51mm NATO round nevertheless met the designers' demands for fully automatic reliability with a full-power round. It remains the main medium machine gun and general-purpose machine gun round for almost all NATO forces, even being used in adapted versions of older .30-06 Springfield machine guns, such as the WWII-era Browning M1919A4. The .303 British Bren gun was also converted to fire the 7.62×51mm NATO round, and the converted weapon was reclassified as the L4 Light machine gun. West Germany rechambered many of its WW2-era MG42s to create the MG2, and the succeeding MG3 is essentially a slightly modified version of the same weapon. These have been largely replaced in the light machine gun role by 5.56×45mm NATO weapons, such as the widespread use of the M249 SAW. However, the 7.62×51mm NATO fully powered cartridge is still the standard chambering for the M134 Minigun and GPMGs such as the M60E4, FN MAG/M240, HK21, MG3, AA-52, Vektor SS-77, UKM-2000 and MG5 and flexible mountings such as helicopters, jeeps, and tanks. It is also commonly found in coaxial mount applications, such as parallel to the main gun on tanks. The characteristics of 7.62 mm bullet types were not only researched in the 20th century but were also studied in the 21st century.
Post-2010 developments