7.62×51mm NATO

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7.62×51mm NATO
NATO 7.62x51.jpg
7.62×51mm NATO rounds compared to AA (LR6) cell.
TypeRifle
Place of origin United States
Service history
In service1954–present
Used byUnited States, NATO, others.
WarsVietnam War, Falklands Conflict, The Troubles, Gulf War, War in Afghanistan, Iraq War, Libyan civil war, among other conflicts
Specifications
Parent case.308 Winchester (derived from the .300 Savage)
Case typeRimless, Bottleneck
Bullet diameter0.308 in (7.82 mm)
Neck diameter0.345 in (8.8 mm)
Shoulder diameter0.454 in (11.5 mm)
Base diameter0.470 in (11.9 mm)
Rim diameter0.473 in (12.0 mm)
Rim thickness0.050 in (1.3 mm)
Case length2.015 in (51.2 mm)
Overall length2.750 in (69.9 mm)
Rifling twist1 in 12 in (30 cm)
Primer typeLarge Rifle
Maximum pressure60,191 psi (415.00 MPa)
Ballistic performance
Bullet weight/typeVelocityEnergy
147 gr (10 g) M80 FMJ2,733 ft/s (833 m/s)2,437 ft·lbf (3,304 J)
175 gr (11 g) M118 Long Range BTHP2,580 ft/s (790 m/s)2,586 ft·lbf (3,506 J)
Test barrel length: 24 inches (61 cm)
Source(s): M80: Slickguns,[1] M118 Long Range: U.S. Armorment[2]
 
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7.62×51mm NATO
NATO 7.62x51.jpg
7.62×51mm NATO rounds compared to AA (LR6) cell.
TypeRifle
Place of origin United States
Service history
In service1954–present
Used byUnited States, NATO, others.
WarsVietnam War, Falklands Conflict, The Troubles, Gulf War, War in Afghanistan, Iraq War, Libyan civil war, among other conflicts
Specifications
Parent case.308 Winchester (derived from the .300 Savage)
Case typeRimless, Bottleneck
Bullet diameter0.308 in (7.82 mm)
Neck diameter0.345 in (8.8 mm)
Shoulder diameter0.454 in (11.5 mm)
Base diameter0.470 in (11.9 mm)
Rim diameter0.473 in (12.0 mm)
Rim thickness0.050 in (1.3 mm)
Case length2.015 in (51.2 mm)
Overall length2.750 in (69.9 mm)
Rifling twist1 in 12 in (30 cm)
Primer typeLarge Rifle
Maximum pressure60,191 psi (415.00 MPa)
Ballistic performance
Bullet weight/typeVelocityEnergy
147 gr (10 g) M80 FMJ2,733 ft/s (833 m/s)2,437 ft·lbf (3,304 J)
175 gr (11 g) M118 Long Range BTHP2,580 ft/s (790 m/s)2,586 ft·lbf (3,506 J)
Test barrel length: 24 inches (61 cm)
Source(s): M80: Slickguns,[1] M118 Long Range: U.S. Armorment[2]

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; a slightly more powerful round.

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 rifles, 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 enough that they can be loaded into rifles chambered for the other round, but .308 cartridges are typically loaded to higher pressures than 7.62x51mm cartridges for use in long-distance hunting of big-game animals. Even though the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) does not consider it unsafe to fire the commercial round in weapons chambered for the NATO round, there is significant discussion[3][4][5] about compatible chamber and muzzle pressures between the two cartridges based on powder loads and wall thicknesses on the military vs. commercial rounds. While the debate goes both ways, the ATF recommends checking the stamping on the barrel; if you're unsure, consult the maker of the firearm.[6][7]

Overview[edit]

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[edit]

Velocity comparison between the 7.62×51mm NATO, .30-06 Springfield, and .300 Winchester Magnum for common bullet weights.

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.

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

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 (9.5 g) bullet at 2,750 feet per second (840 m/s) but was approximately 12 inch (13 mm) 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.

Comparison of 7.62 mm NATO, 5.56 mm NATO and 9 mm 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 bipods or heavier barrels.

While this was going on, the U.S. Project SALVO concluded that a burst of four rounds into a 20-inch (51 cm) 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.

RifleCartridgeCartridge weightWeight of loaded magazine10 kg (22#) ammo load
M147.62×51mm393 grains (25.5 g)20 rds @ 0.68 kg14 mags / 280 rds
M165.56×45mm183 grains (11.9 g)20 rds @ 0.3 kg33 mags / 660 rds
AK-477.62×39mm281 grains (18.2 g)30 rds @ 1.2 kg*[8]8 mags / 240 rds

(*AK-47 magazines are much heavier than 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, 7.62×51mm 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 200 ft/s (61 m/s) faster than the M118LR 175 gr sniping round. However, the M80 drops to subsonic velocity around 875 m (957 yd), while the initially slower M118LR is supersonic out to 950 m (1,040 yd) due to its low-drag bullet.[9]

The 7.62×51mm NATO and 5.56×45mm NATO cartridges compared to an AA battery.

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 114.5 grains (7.4 g) of lead with production of each M80A1 projectile. Fielding is expected for 2014.[10]

Military cartridge types[edit]

Three recovered 7.62×51mm NATO bullets (next to an unfired cartridge (Tracer ammunition), showing rifling marks
7.62mm, NATO, Orange-tipped tracer ammunition, M62: 142-grain (9.2 g) tracer cartridge.
The 7.62mm M118 long range cartridge.

Department Of Defense Identification Codes (DODIC)[edit]

This US Armed Forces and NATO code is used to identify the cartridge, the cartridge type, and the packing method (carton, clips, link belt, or bulk) used.

See also[edit]

References[edit]

External links[edit]