Introduced in 1979, the AC-556 is a selective-fire version of the Mini-14 marketed for military and law enforcement use. The design incorporates a selector on the right/rear of the receiver to select either semi-automatic, 3-round burst, or full-automatic fire modes; the manual safety at the front of the trigger guard operates the same as a standard Mini-14. The front sight is winged and incorporates a bayonet lug. The or barrel incorporates a flash suppressor, which can be used to launch approved tear-gas and smoke rifle grenades. A folding stock was used on the AC-556F and AC-556K. The rifle came equipped with 20-round magazines and a 30-round version was available for a time. The AC-556 was dropped from production in 1999 and Ruger stopped offering service for the rifle in 2009. By that time, some models became available for private civilian purchase in the NFA market.