Semi-automatic rifles, including versions of the AR-15, and autoloading rifles limited to firing single shots with each pull of the trigger and are not assault rifles as they are not selective fire.
Assault weapons are primarily limited to the United States, the term assault weapon is a political term, separate from the military definition, used to describe a variety of semi-automatic firearms that have certain, mostly cosmetic features associated with military or police tactical firearms.
The 1994 Federal Assault Weapons Ban, which expired on September 13, 2004, defined the rifle type of assault weapon as a semiautomatic firearm with the ability to accept a detachable magazine, and two or more of the following:
1. Folding or telescoping stock,
2. Conspicuous pistol grip,
4. Flash suppressor, or threaded barrel designed to accommodate one,
5. Grenade launcher.
A common public misconception persists that the assault weapons ban restricted weapons capable of fully automatic fire, such as assault rifles and machine guns. Fully automatic weapons, however, were unaffected by the ban, and have been continuously and heavily regulated since the National Firearms Act of 1934. Subsequent laws such as the Gun Control Act of 1968 and the Firearm Owners Protection Act of 1986 also affected the importation and civilian ownership of fully automatic firearms.
An assault rifle is a selective fire (semi-auto / full-auto) rifle or carbine, categorized between light machine guns which fire a rifle cartridge, and submachine guns which fire a handgun cartridge rather than a rifle cartridge. Assault rifles include the M16 rifle, M4 carbine and AK-47. Assault rifles are the standard small arms in most modern armies, having replaced larger, more powerful battle rifles, such as the World War II-era M1 Garand and Tokarev SVT.
A machine gun is a fully-automatic mounted or portable firearm, usually designed to fire rifle cartridges in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred bullets per minute. Belt-fed weapons or rifles with very limited capacity fixed magazines are also generally not assault rifles.