I remember hearing back in the early 70s they may have tested it, along with the Stoner and other weapons, but not seriously. As for actual issue, no, not that I've ever heard, the Mini-14 has always been a police/civilian weapon.
The actual M-14 it's modeled after was in general service for the Army, Marines and Navy (and still in limited use today in very small numbers, like in Afghanistan) from 1957-65, though some stayed in service later (my father deployed to Vietnam with an M14 in 1968 and everyone there had M16s already...he kept it about five months then they made him give it back).
The Mini-14 is used by the French Gendarmerie (state police), the Royal Ulster Constabulary, and most sheriff's departments in the U.S. But even in full-auto AC556 configuration I can't remember any military using it as a general issue weapon.