The M16A2 service rifle is a lightweight air-cooled, gas-operated, magazine-fed shoulder weapon. It fires a 5.56 mm ball projectile at a muzzle velocity of 2,800 feet per second. This is my rifle. Repeat after me.
— Anthony "Swoff" Swofford, Jarhead
The M16 (officially Rifle, Caliber 5.56 mm, M16) is the United States military designation for the AR-15 rifle adapted for semi-automatic, three-round burst and full-automatic fire. Colt purchased the rights to the AR-15 from ArmaLite, and currently uses that designation only for semi-automatic versions of the rifle.