The Ontos, officially the Rifle, Multiple 106 mm, Self-propelled, M50, was an American light armored tracked anti-tank vehicle developed in the 1950s. It mounted six M40

M40 recoilless rifle

The M40 recoilless rifle was a lightweight, portable, crew-served 105 mm weapon intended primarily as an anti-tank weapon made in the United States...

 106 mm recoilless rifle

Recoilless rifle

A recoilless rifle or recoilless gun is a lightweight weapon that fires a heavier projectile than would be practical to fire from a recoiling weapon of comparable size. Technically, only devices that use a rifled barrel are recoilless rifles. Smoothbore variants are recoilless guns...

s as its main armament, which could be fired in rapid succession against single targets to guarantee a kill.

Originally conceived as a fast tank killer, it was employed by US Marines who consistently reported excellent results when used for direct fire support against infantry during the Vietnam War

Vietnam War

The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...

.