When extra range or firepower is needed, RAINBOW turns to Colt's M16 Weapon System. 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 1.5x low-power optical sight and single, and three round burst trigger group on the standard issue A2, and a RISS mounted 3.5x35 Trijicon ACOG scope with single and full-auto trigger group on the updated A4 variant. 