USA M50, Ontos 106mm, Self-Propelled Antitank Gun Ontos is Greek for “The Thing.”

The M50 is a light, mobile antitank system mounting six 106mm recoilless rifles. The Ontos was developed in the mid 1950s and designed for direct sea to land invasion. It was adopted by the U.S. Marine Corps and saw service in Vietnam. Its primary design flaw was that the recoilless rifles could only be reloaded from the outside of the vehicle.