Sorry it took so long to get back to this thread, real life kept me busy The Ontos also referred to as the thing was developed for use by the US Army in the 50's to ward of an anticipated Russian armored attack in Europe during the cold war. The designated for the Ontos is the M50, the M40A1 I referred to in the title is the recoilless rifles. This vehicle made significant contributions to the Marine and Army infantry during the Viet Nam War, only about 176 were known to have been in the Marine armored divisions.

The Ontos has six, 106 M40A1 recoilless Rifles and four spotter 50 cal. guns on on each of the top two rifles on either side, plus a 50 or 30 cal machine gun mounted on the weapons bar. The two lower Recoilless Rifles could be removed in needed and replaced on ground mounts. It served the Marine Corp from the 1950's to 1970 when they were dismembered. The Ontos did not see combat until April of 1965 against Dominican rebels, then again in Vietnam.

The Ontos had a three man crew, driver, commander/gunner and loader. The Ontos was also called "The Pig", when it was hot and humid the crew would open the back doors of the unit, the dust from the tracks would swirl up into the crew compartment and they would come out covered with dirt and sweat, thus it was called "Pig".

The worst enemy of the Ontos was the land mine, they took out more than any other action. One Ontos crew member stated that land mines took out 4 of 5 M50's during his 13 months in Vietnam.