machine gun

According to the ATF, A firearm designed fire more than one bullet with a single pull of the trigger. They are highly regulated and require a lot of expensive bureacratic paperwork and a squeaky-clean record to acquire the Class III Federal Firearms License needed to legally own one. The M-16A2 would technically fall under this category because of its ability to fire in 3-round bursts. AR-15s, civilian semiauto AK-47 clones, etc, ARE NOT MACHINE GUNS. The most common AK-47 variant in the US civilian market is the Romanian-built WASR-10, imported by Century Arms, because it is the least expensive AK. Although similar in appearance, they DO NOT fit the definition of MACHINE GUN because they fire one and only one round with a single pull of the trigger, which means they are semi-automatic. An AR-15, despite its similarity to an M-16, is not the same thing. Vietnam-era M-16s were true MACHINE GUNS also, capable of fully automatic fire. The Pentagon brass found this to be a waste of ammo and restricted later models to 3 round burst mode as the only option for selective fire.