Ruger introduced their semiauto Mini-14 rifle in 1973, and followed it in 1979 with the AC-556, a select-fire version intended for military and police sales. Offered with either an 18.5 inch barrel and solid wood stock or a 13 inch barrel and side folder, the AC-556 incorporated a selector switch on the back of the receiver to change between semiauto, 3-round burst, and fully automatic modes. Like some burst mechanisms, the Ruger model did not reset after each firing, and the round counter increments with every shot in any mode. As a result, when switching to burst, the first burst fired is unpredictable, and may be 1, 2, or 3 rounds.
A fair number of small sales of the AC-556 were made to police and small security agencies, especially those who wanted a gun more “friendly” looking than a black AR-15. A few international military sales were made, the most significant being a licensing deal with the French security services that led to the Mousqueton AMD, a slightly changed copy of the AC-556 for French police. Although Ruger did not sell them directly to civilians, gun made between 1979 and 1986 were transferrable, and many have been sold out of police inventory onto the commercial market. Ruger discontinued sales in 1999, and ceased factory repair service of them in 2009.