A genuine assault weapon, as opposed to a legal definition, is a hand-held, selective fire weapon, which means it's capable of firing in either an automatic or a semiautomatic mode depending on the position of a selector switch. These kinds of weapons are heavily regulated by the National Firearms Act of 1934 and are further regulated in some states.
A fully automatic weapon (a machine gun) is one that fires a succession of bullets so long as the trigger is depressed or until the ammunition supply is exhausted. In addition, any weapon that shoots, is designed to shoot, or can be readily restored to shoot automatically, more than one shot at a time by a single trigger pull, is legally considered to be a machine gun.
Submachine guns are fully automatic weapons that fire a handgun cartridge and can be operated by one person. Sometimes they are referred to as machine pistols.
A machine gun can normally fire between 400 and 1,000 rounds (bullets) per minute, or between 7 and 17 rounds per second.
A semi-automatic firearm, or self-loading firearm is a firearm which performs all steps necessary to prepare the weapon to fire again after firing--assuming rounds remain in the weapon's feed device or magazine.
Typically, this includes extracting the spent cartridge case from the weapon's firing chamber, ejecting spent cartridge cases from the weapon, re-cocking the firing meachnism, and loading a new cartridge into the firing chamber. Although automatic weapons and selective fire firearms do the same tasks, semi-automatic firearms do not automatically fire an additional round until the trigger is released and re-pressed by the person firing the weapon.
