The AR15 is the variant of the M16 and A4 used by law enforcement and military

The AR15 is the citizen version of the M16 and A4 and other similar weapons used in combat and law enforcement situations. These are all called Black Weapons. They are the backbone of the American assault rifle weapon platform. Semi-Auto AR weapons are legal to own. The M16 and other fully automatic weapons most usually require a dealer with a class 3 license to purchase, they are not illegal to own but are illegal on your local shooting range. So the AR is King to the average Black Weapon Rifle owner.