7 . 62×51mm NATO The 7 . 62×51mm NATO ( official NATO nomenclature 7 . 62 NATO ) is a rifle cartridge developed in the 1950s as a standard for small arms among NATO countries . It should not be confused with the similarly named Russian 7 . 62×54mmR cartridge . It was introduced in U . S . service in the M14 rifle and M60 machine gun in the late 1950s . The M14 was superseded in U . S . service as the infantry adopted the 5 . 56×45mm NATO M16 . However , the M14 and many other firearms that use the 7 . 62×51 round remain in service , especially in the case of sniper rifle s , machine guns , and as the service weapon chosen by special operations forces . 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 . 62×51mm NATO and the commercial . 308 Winchester cartridges are similar , and even though the Sporting Arms and Ammunition Manufacturers ' Institute ( SAAMI ) does not consider it unsafe to fire the NATO round in weapons chambered for the commercial round , there is 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 . The debate goes both ways , the ATF recommends checking the stamping on the barrel ; if you ' re unsure , consult the maker of the firearm . 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 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 . Development . Work that would eventually develop the 7 . 62×51mm NATO started just after World War I 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 appeared to be looming again only a few decades later , the . 30 - 06 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 served well beyond the Korean War and into the mid - 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 8 - round 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 bullet at but was approximately shorter . The eventual result of this competition was the T44 rifle . 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 for emergencies only and continue to use semi - automatic fire 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 . The British did start introducing the . 280 along with the " bull - pup " Rifle No . 9 , but the process was stopped in the interests of harmonization across NATO . The T65 was chosen as the NATO standard cartridge in 1954 . 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 . The T44 was adopted as the M14 in 1957 . Britain and Canada adopted the Belgian 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 . 62 mm NATO could not be fired controllably in fully automatic because of 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 to improve control with bipod s or heavier barrel s . 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 " ) , while other researchers investigated the promising flechette rounds that were 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 overall length was not well suited for jungle warfare . Also , the weight of 7 . 62×51mm 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 assault rifles , which the Vietcong and North Vietnamese Army soldiers 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 , which caused 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 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 . 56×45mm ammunition as 7 . 62×51mm for the same weight , which allowed them an advantage against a typical N . V . A . unit armed with Type 56 - 1s . 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 . 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 at long ranges , and has since found popularity as a sniping round . For instance , M14 variants such as the Mk 14 Enhanced Battle Rifle and M25 Sniper Rifle were utilized 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 . Specialized loadings were created for 7 . 62×51mm NATO - chambered sniper rifles . They used heavier and more streamlined bullets that had a higher ballistic coefficient than standard ball rounds , meaning they shed velocity at longer ranges more gradually . Loss of 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 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 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 have been replaced to a considerable extent in the light machine gun role by 5 . 56×45mm NATO weapons , such as the widespread use of the M249 SAW , but the 7 . 62 round is still the standard chambering for most general - purpose machine guns such as the M60E4 , the M240 and the German HK21 and MG3 , and flexible mountings such as helicopters , jeeps , and tanks . The U . S . Army is developing an improved version of the M80 ball 7 . 62 mm round , called the M80A1 . The M80A1 incorporates changes found in the M855A1 5 . 56 mm round . Like the M855A1 , the M80A1 is expected to have better hard - target penetration , more consistent performance against soft targets , and significantly increased distances of these effects over the M80 . The bullet is redesigned with a copper jacket and exposed hardened steel penetrator , eliminating of lead with production of each M80A1 projectile . Fielding is expected for 2014 .