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 106 mm manually loaded M40 recoilless rifles as its main armament, which could be fired in rapid succession against single targets to increase the probability of a kill. Although the actual caliber of the main guns was 105 mm, it was designated 106 mm to prevent confusion with the ammunition for the 105 mm M27 recoilless rifle, which the M40 replaced.

It was produced in limited numbers for the U.S. Marines after the U.S. Army cancelled the project. The Marines consistently reported excellent results when they used the Ontos for direct fire support against infantry in numerous battles and operations during the Vietnam War. The American stock of Ontos was largely expended towards the end of the conflict and the Ontos was removed from service in 1969.

Several variants were also studied. The Utility Vehicle, Tracked, Infantry, T55 was a light Armored personnel carrier (APC), but only two versions of the prototype were built. It proved impractical due to the limited room inside, carrying only five infantry and forcing the driver to lie prone. A "stretched" version known as the Utility Vehicle, Tracked, Infantry, T56 was also built, and while it held a complete eight-man team, their equipment had to be carried on the outside. Neither was considered very useful.

In 1960 there was a brief study made to replace the Ontos's 106 mm rifles with a new 105 mm design that included a revolver-style autoloader. This project was not accepted.

Another proposed upgrade was replacing the GMC engine with a newer Chrysler 361 cu in (5.92 L) V8 engine. This upgrade was implemented and the variant was named Rifle, Multiple 106 mm, Self-propelled, M50A1. However of the 297 vehicles initially accepted by the Marines, only 176 were converted between 1963 and 1965 to this standard.

Pictured here is a 1:72 scale replica of a USMC Ontos Rifle, Multiple 106mm, Self-Propelled, M50A1 recoilless tank destroyer nickaned "Road Runner", which now resides at The US Army Armour and Calvary Collection, in Fort Benning, Georgia. Pre-order! Ship Date: October 2024.

Dimensions:
Length: 5-inches
Width: 2-inches

Release Date: ?

Historical Account: "The Hue Forward" - While the M50 was designed as a tank destroyer, during the Vietnam War most M50s did not engage enemy armor as the North Vietnamese Army deployed few tanks. The Ontos was therefore more widely used by the US Marines for direct fire support for the infantry in combat, a role that was never emphasized in training or doctrine. Its light armor was effective against small arms but vulnerable to mines and Rocket-propelled grenades. Consequently, many Ontos were deployed in static defense positions.

The relatively light weight of the M50 made it exceptionally mobile for the amount of firepower it carried. In one operation, the Ontos was the only tracked vehicle light enough to cross a pontoon bridge. In the Battle of Hue, Colonel Stanley S. Hughes felt the Ontos was the most effective of all Marine supporting arms. At ranges of 300 to 500 yards (270 to 460 m), its recoilless rifles could knock holes in or completely knock down walls. The appearance of an Ontos was sometimes enough to make the enemy break and run, and anecdotal accounts describe the enemy fleeing occupied buildings when an Ontos's spotting round entered a window. In Operation Desoto, the introduction of the large CH-53 Sea Stallion helicopter made possible moving a platoon 25 miles (40 km) south of Quang Ngai City carrying Ontos in slings underneath the aircraft.

The Ontos units were deactivated in May 1969, and some of the vehicles were handed over to an Army light infantry brigade. They used them until they ran out of spare parts, and then removed the turrets and used them as fixed fortifications. Both these and the rest of the vehicles returned from Vietnam in 1970 and were cut up for scrap, with some of the chassis being sold off to be converted into construction vehicles. Some of the Ontos that were sold to construction companies were later acquired by collectors for restoration.

The Ontos did see use as an anti-tank weapon during the American involvement in the Dominican Civil War: on April 29th, 1965, an M50 Ontos and an M48 Patton of the 6th MEU engaged and destroyed two rebel L/60L light tanks, each destroying one. In another instance, an Ontos destroyed an AMX-13.