High Quality Content by WIKIPEDIA articles! The Ford MGM-51 Shillelagh was an American anti-tank guided missile designed to be launched from a conventional gun (cannon). It was originally intended to be the medium-range portion of a short, medium, long-range system for armored fighting vehicles in the 1960s and `70s to defeat future armor without an excessively large gun. Developing a system that could fire both shells and missiles reliably proved complex and largely unworkable. It served most notably as a primary weapon of the M551 Sheridan light tank, but the missile system was deleted from units serving in Vietnam. Ultimately very few of the 88,000 rounds produced were ever fired in combat.