AR-15 (for Armalite model 15, often mistaken for Assault Rifle)'s the common name for the widely-owned semi-automatic rifle which soon afterwards became the fully automatic M16 and M4 carbine assault rifles, which are currently in use by the United States military. AR-15 was the original name for what became the militarily designated M16, the assault rifle first used by the U.S. in the Vietnam War. The name AR-15's now used almost exclusively to refer to the semi-automatic (commercially availab… (More on Ar-15)