M56 Scorpion

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M56 Scorpion
M56 at AAF Tank Museum.JPG
M56 Scorpion preserved at the American Armored Foundation Tank Museum in Danville, Virginia.
Type Self-propelled gun
Place of origin United States
Service history
Used by See users
Wars Vietnam War
Production history
Manufacturer Cadillac Motor Car Division of General Motors
Produced 1953–1959
Weight 7.1 tonnes (16,000 lb)
Length 4.55 metres (14 ft 11 in) (excluding gun)
Width 2.57 metres (8 ft 5 in)
Height 2 metres (6 ft 7 in) over gun shield
Crew 4 (commander, gunner, loader and driver)

Armor unarmored except for blast shield
90 mm M54 Gun
29 rounds
Engine Continental A01-403-5 gasoline engine
200 brake horsepower (150 kW)
Transmission Allison CD-150-4, 2 ranges forward, 1 reverse
Suspension Torsion tube over bar at wheels 1 and 4, torsion bar at wheels 2 and 3
Ground clearance 0.32 m (1 ft 1 in)
Fuel capacity 210 litres (46 imp gal; 55 US gal)
230 kilometres (140 mi)
Speed 45 kilometres per hour (28 mph)

The M56 Scorpion was an unarmored American self-propelled anti-tank gun, which featured a 90mm M54 gun with a simple blast shield, and unprotected crew compartment. It was meant to be transported by helicopter or by air drop.


The M56 was manufactured from 1953 to 1959 by the Cadillac Motor Car Division of General Motors for use by US airborne forces, though the vehicle was eventually used by the Spanish Navy Marines, Morocco and the Republic of Korea as well. With a crew of four (commander, gunner, loader and driver), the M56 weighed 6.4 tonnes (14,000 lb) empty and 7.7 tonnes (17,000 lb) combat-loaded. It had infrared driving lights but no Nuclear, Biological and Chemical (NBC) protection system and was not amphibious.

The M56 was a fully tracked vehicle with rubber-tired run-flat road wheels and front drive sprocket wheels. It was powered by a Continental A01-403-5 gasoline engine developing 200 brake horsepower (150 kW) at 3,000 rpm, allowing a maximum road speed of 28 miles per hour (45 km/h) and a maximum range of 140 miles (230 km). Twenty-nine rounds of main gun ammunition were carried, and only the blast shield was armored.

In service[edit]

The M56 saw combat service with U.S. forces in the Vietnam War. It was deployed with the 173rd Airborne Brigade, which was the only Airborne Brigade deployed with the M56,[1] where it was used mainly in a direct fire-support role. Its function as an air portable, self-propelled, anti-tank vehicle was eventually replaced in Vietnam by the troubled but effective M551 Sheridan which had a fully armored turret. The USMC used the Ontos, which had an armored cabin and was armed with recoilless rifles, in a similar role (the running gear of the first Ontos prototype was the same as on the M56, but it was replaced for the production variant).

With the retirement of the Sheridan, current US airborne troops did not have a self-propelled gun system that could be delivered by air drop until the development of the Stryker MGS variant that is currently undergoing airdrop certification.



  • A well preserved M56 can be found in a city park in Auburn, Washington.
  • An M56 is on display as a memorial in Tillicum Park. Forks, Washington.
  • An M56 is on display next to a park in Elmwood Park, New Jersey.
  • A restored M56 is on display at the American Armored Foundation Tank Museum in Danville, Virginia, along with a diorama of a destroyed M56.
  • An M56 is on display (along with an M60 tank) in front of the Duluth, Georgia American Legion post.
  • An M56 is on display (along with an M41 Walker Bulldog) outside Veterans Memorial Stadium in Cedar Rapids, Iowa.
  • An M56 Scorpion is on Outdoor Display at the 82nd Airborne War Memorial Museum at Ft. Bragg, N.C.
  • An M56 is on display at the American Legion Post in Guntersville, AL.
  • An M56 Scorpion is on display at the Boyd County War Memorial in Armco Park in Summit, KY.
  • An M56 arrived at Forest Hill Station, home of the U.S. Army Cadet Corps in Millersburb, KY, on July 19th, 2012.
  • An M56 Scorpion is on display in front of VFW Post 2524 Culpeper VA.
  • An M56 Scorpion is on display at the Iowa Gold Star Museum at Camp Dodge in Johnston, Iowa.
  • An M56 Scorpion is on display in the Military Vehicle Technology Foundation's facility in Portola Valley, in California. However, it will soon be relocated to the Collings Foundation in Stow, Massachusetts.
  • An M56 Scorpion is on display at the 45th Infantry Museum in Oklahoma City, OK.
  • An M56 Scorpion is on display at Ft Sill, Oklahoma.
  • An M56 Scorpion is on display in front of the American Legion Hall, Post 88, in Donelson Tennessee.
  • An M56 Scorpion is on display at Camp Mabry in Austin, Texas.
Diorama of destroyed M56 at the AAF Tank Museum. Note the prominent rubber tires on the road wheels.

See also[edit]


  • Foss, Christopher F. (1974) [1972]. Jane's Pocket Book of Tanks and Armored Fighting Vehicles. Collier Books. p. 153. LC Control No. 73-15286. 
  • Trewhitt, Philip (1999). Armored Fighting Vehicles. New York, NY: Amber Books. p. 126. ISBN 0-7607-1260-3. 

External links[edit]