5.56 x 45 mm NATO

5.56 mm NATO, designated STANAG 4172, is the standard rifle ammunition for NATO forces. It is derived from, but not entirely interchangable with, the .223 Remington cartridge.

History

The previous standard NATO round was the 7.62 mm (based on the .30 rifle cartridge). At the time of selection, there had been criticism that the 7.62 x 51 mm round was overpowered for modern assault rifles, and smaller alternatives had been tendered. These doubts would later be shown to be well-founded.

Related Topics:
7.62 x 51 mm - Assault rifle

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During the late 1950s, ArmaLite and other US firearm designers started their individual Small Caliber/High Velocity (SCHV) assault rifle experiments using the commercial .222 Remington cartridge. When it became clear that there was not enough powder capacity to meet U.S. Continental Army Command's (CONARC) velocity and penetration requirements, ArmaLite contacted Remington to create a similar cartridge with a longer case body and shorter neck. This became the .222 Remington Special. At the same time, Springfield Armory's Earle Harvey had Remington create an even longer cartridge case then known as the .224 Springfield. Springfield was forced to drop out of the CONARC competition, and thus the .224 Springfield was later released as a commercial sporting cartridge known as the .222 Remington Magnum. To prevent confusion with all of the competing .222 cartridge designations, the .222 Remington Special was renamed the .223 Remington. After playing with their own proprietary cartridge case design, the .224E1 Winchester, Winchester eventually standardized their case dimensions, but not overall loaded length, with the .222 Remington Special to create a cartridge known as the .224E2 Winchester. With the US military adoption of the ArmaLite AR-15 as the M16 rifle in 1963, the .223 Remington was standardized as the 5.56x45 mm. However, the .223 Remington was not introduced as a commercial sporting cartridge until 1964.

Related Topics:
ArmaLite - Earle Harvey - M16

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During the 1970s, NATO members signed an agreement to select a second, smaller caliber cartridge to complement the 7.62 mm NATO. Of the cartridges tendered, the 5.56 mm was successful, but not the 5.56 loading as used by the US at that time. Instead, the Belgian FN SS109 loading was chosen for standardization. The SS109 used a heavier bullet at a lower muzzle velocity for better long-range performance.

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The cartridge is 57 mm (approximately 2.25 inches) long and 9.7 mm (0.38 inches) in diameter. The bullet itself is 0.75 inches (20 mm) long and 0.224 inches (5.7 mm) in diameter.

Related Topics:
Cartridge - Bullet

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The .223 Remington cartridge has the same dimensions as the 5.56x45, but (generally) has a lower propelling charge, the NATO loading being the more powerful. Chambering and firing a 5.56x45 round in a .223 rifle is possible, but not always wise. However, it is safe, if not always effective, to fire a .223 Remington round from firearms designed for the 5.56.

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