An assault rifle most commonly used by Law Enforcement and Military. The AR15 uses the .223 Caliber (NATO 5.56).
During the North Hollywood shoot-out between the two gunmen armed with AK-47s and Body Armour. The LAPD had no tactical advantage against the two gunmen with their puny ass 9mm pistols. They went to a local gunshop and snagged some AR15s and shot the gunmen down since their body armour couldn't stop it.