Colt / FN Herstal

The M4A1 is a fully automatic variant of the M4 carbine, a shorter and lighter version of the M16A2 assault rifle. It fires the 5.56×45mm NATO round and is the primary service rifle for many U.S. military units.

The M16 is a family of military rifles adapted from the ArmaLite AR-15 rifle for the United States military. It is a lightweight, 5.56×45mm NATO, air-cooled, gas-operated, magazine-fed assault rifle.