Today in WW II: 20 Jun 1943 Operation TOENAILS opens with Marines landing at Segi Point on Vangunu Island, southeast of New Georgia.  

Rifle, Self Propelled, Full Tracked, Multiple 106mm M50 and M50A1

The Ontos is a lightly-armored, tracked antitank vehicle carrying six 106mm recoilless rifles. Its full nomenclature is "Rifle, Self Propelled, Full Tracked, Multiple 106mm M50 and M50A1." Both the M-50 and M-50A1 variants were produced for the U.S. Marine Corps. The word Ontos comes from Greek, meaning "the thing."

The first combat use of the Ontos was in the summer of 1958 during a Marine Corps intervention in Lebanon. Ontos provided suppressive fire and counter-sniper fire in urban areas, a rehearsal for tactics later used in Vietnam.

Ontos was used very effectively in Vietnam. Its light weight and maneuverability made it available for combat in situations where tanks and other guns could not operate. During the March 1968 Battle of Hue, part of the Tet Offensive, the USMC Ontos provided direct fire to suppress enemy positions and to blow holes in the buildings so the Marines could advance. They were also extremely useful for providing suppressive fire and as counter-sniper weapons.

Ontos was disliked by its crews because they had to load and fire the recoilless rifles from an exterior, exposed position. The massive backblast also made it easy for enemy gunners to locate the Ontos.

The Ontos was deactivated by the USMC in May 1969 but some serviceable vehicles were transferred to a US Army Light Infantry Brigade where they were used for approximately one year. Civilian agencies of the US Government received a few de-mil Ontos, using them as forestry or construction vehicles. A small number were sold to collectors and museums (or transferred to service museums) where they have been preserved.

Find additional photos and hi-res versions of the M-50 Ontos at the Olive-Drab Military Mashup.

M-50 Ontos manuals:

  • TM 9-7222 Technical Manual, June 1957
  • TM 9-2350-212-12 Operator's and Organizational Maintenance Manual, December 1959
  • TM 9-2350-212-35 Ordnance Field and Depot Maintenance, September 1958

M50 Ontos Photos Gallery

M-50 Ontos
M-50 Ontos.

Ontos on Chu Lai beach, Vietnam, 1 June 1965.  Photo taken shortly after descending from landing craft aboard the USS Thomaston (LSD 28)
Ontos on Chu Lai beach, Vietnam, 1 June 1965. Photo taken shortly after descending from landing craft aboard the USS Thomaston (LSD 28).

USMC M-50 Ontos.  One 106mm round is on the front slope
USMC M-50 Ontos. One 106mm round is on the front slope.

M-50 Ontos
M-50 Ontos.