Assault Rifle - 5.56mmx45 - U.S. - 700 RPM - When extra range or firepower is needed, RAINBOW turns to Colt's M16A2. Tried and true, it's 5.56 caliber easily pierces Level II body armor and has the longest range of any of RAINBOW's standard weapons. It comes standard with a low-power holo-sight and single, three round, and full-auto trigger group. 