The Ontos, officially the Rifle, Multiple 106 mm, Self-propelled, M50, was a U.S. light armored tracked anti-tank vehicle developed in the 1950s, a fast tank killer for airborne forces.It mounted six M40 106 mm recoilless rifles as its main armament, which could be fired in rapid succession against single targets to guarantee a kill. It was produced in limited numbers for the U.S. Marines after the U.S. Army lost interest in the project.