An AR15 is a semi-automatic rifle. An M-16 is an automatic rifle and can't be owned by a civilian. A semi-automatic firearm means to fire two rounds you must pu

An AR15 is a semi-automatic rifle. An M-16 is an automatic rifle and can't be owned by a civilian. A semi-automatic firearm means to fire two rounds you must pull the trigger twice, to fire three you pull three times etc. An automatic rifle will fire as long as you hold the trigger back. An M-16 will expend it's 30 round magazine in about 3 seconds in full auto. Full auto is rarely used and when it is it's mainly for suppressive fire, which generally means to keep the enemy's head down while your squad moves to better cover or firing position. Oh, one more thing, at house distances shotguns most certainly have to be aimed.