An AR-15 style rifle is a lightweight semi-automatic rifle based on the Colt AR-15 design. After Colt’s patents expired in 1977, an expanded marketplace emerged with many manufacturers producing their own version of the AR-15 design for commercial sale. They are referred to as modern sporting rifles by the National Shooting Sports Foundation, a firearms industry trade association, and by some manufacturers. Coverage of high-profile incidents where various versions of the rifle were involved often uses the shorthand AR-15.
