5.56 x 45 mm NATO, similar to, and thus commonly called the Remington .223 cartridge, is the size of standard rifle ammunition for NATO forces. 5.56 mm amunition was introduced for use in the American M16 rifle in the 1960s. It was used as an alternative to the previous NATO standard ammunition size, 7.62 mm caliber. The cartridge is approximately 2.25 inches (57 mm) long and 0.38 inches (9.7 mm) in diameter. The bullet itself is 0.75 inches (20 mm) long and 0.25 inches (5.56 mm) in diameter.

The 5.56 NATO cartridge will penetrate approximately 15 to 20 inches (380 to 500 mm) in soft tissue, assuming it is a standard military ball projectile being fired; these cartridges, at close range, propel the bullet fast enough so that it yaws early on in penetrating tissue, causing the bullet to fracture and fragment at the cannelure. This is due in part to the rotational energy imparted by the high rate of twist in newer M16 barrels (A1 and later models), and is responsible for the large wound profile generated by this cartridge at close ranges. This phenomenon of hydrostatic shock is at least fairly controversial, but seems to impart much greater damage to tissue than the wound track alone would suggest.

The NATO Ball round (the U.S. M855) can also penetrate up to 3 mm of steel while the Armor-piercing variant (the U.S. M995) can penetrate up to 6 mm.

Weapons using 5.56 mm ammunition include:

• American M16A1/A2/A3/A4, M4/M4A1 Carbine, CAR-15, XM177E1/E2, M733, AR-15, and other rifles of the Armalite family
• American/Belgian M249 SAW / FN Minimi light machine gun
• Austrian Steyr AUG rifle
• Belgian FN FNC and FN F2000 rifles
• British L85/SA80 rifle
• Canadian Diemaco C7/C8 rifles
• French FAMAS F1/G2 rifle
• German Heckler und Koch HK33, Heckler und Koch G36, HK23, and HK53 rifles and machine guns
• Israeli IMI Negev SAW, Galil assault rifle and Tavor TAR-21 bullpup assault rifle
• Russian AK-101 and -105 rifles
• Singaporean SAR-21
• South African Vektor R4 and R5
• South Korean K2 rifle

See also

• Caliber
• 7.62 mm caliber
• .50 BMG
• Table of pistol and rifle cartridges

Sources & External links

• FAS: 5.56 mm Ammunition
• The Gun Zone: 5.56 mm FAQ