1 Answer

Assault weapon is a non-technical term referring to any of a broad category of firearms with certain features, including some semiautomatic rifles, some pistols, and some shotguns. There are a variety of different statutory definitions of assault weapons in local, state, and federal laws in the United States that define them by a set of characteristics they possess. Using lists of physical features or specific firearms in defining assault weapons in the U.S. was first codified by the language of the now-expired 1994 Federal Assault Weapons Ban.sometimes described as military-style features useful in combat.[2] A common usage is to interchange the term with assault rifle, but unlike that term, "assault weapon" has no consistent or specific definition and so is subject to varying definitions for varying purposes, including definitions that include common non-military-style firearms.
The term was most notably used in the language of the now-expired Public Safety and Recreational Firearms Use Protection Act of 1994, more commonly known as the Federal Assault Weapons Ban, which expired in 2004. The federal assault weapons ban specifically prohibited 19 guns considered to be assault weapons. These were all semi-automatic firearms, meaning that they can eject spent shell casings and chamber the next round without additional human action, but (as opposed to automatic firearms) only one round is fired per pull of the trigger. In addition to the 19 weapons specifically prohibited, the federal assault weapons ban also defined as a prohibited assault weapon any semiautomatic rifle with a detachable magazine and at least two of the following five items: a folding or telescopic stock; a pistol grip that protrudes conspicuously beneath the action of the weapon; a bayonet mount; a flash suppressor or threaded barrel (a barrel that can accommodate a flash suppressor); or a grenade launcher. The act also defined as a prohibited assault weapon semi-automatic pistols that weighed more than 50 ounces when unloaded or included a barrel shroud, and barred the manufacture of magazines capable of carrying more than 10 rounds.
Although the federal assault weapons ban expired in 2004, several states have their own assault weapons bans, which sometimes differ from the former federal law. For example, in California, the Roberti-Roos Assault Weapons Control Act of 1989 bars a number of specific firearm models as well as firearms that have one of a number of features.

http://en.wikipedia.org/wiki/Assault_weapon