M55 Self Propelled Howitzer

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M55 8 inch Self-Propelled Howitzer 3.JPG
M55 howitzer in the US Army Ordnance Museum
Type Self-propelled artillery
Place of origin  United States
Service history
In service 1970s (Belgium)
Used by  United States
Wars Vietnam War
Production history
Manufacturer Pacific Car and Foundry Co.
Produced 1950s
Weight 44 metric tons
Length 9.75 m
Crew 6

Armour 25 mm (maximum)
(Rolled homogeneous armour)
203.2 mm M47 howitzer
(10 rounds)
.50 cal M2HB machine gun
(900 rounds)
Engine Continental AV-1790-5B
(12 cylinder, 4 cycle, 90° vee gasoline)
810 hp at 2800 rpm (gross)
704 hp at 2800 rpm (net)
Transmission Allison CD-850-4A
(two ranges forward, one reverse)
Suspension torsion bar
160 mi (260 km)
Speed 30 mph (48 km/h)

The M55 was an American fully enclosed and armored self-propelled artillery based on the M53 155 mm assault gun. It had a 203.2 mm (eight inch) howitzer which could traverse 30° left or right, carrying only 10 rounds of ammunition. The gun had a maximum range of 16,916 meters (10.51 miles) with a rate of fire of one round every two minutes. The M55 armor was light, 25 mm maximum, but sufficient to protect the crew from indirect artillery hits or small arms fire.

The M55 used components of the M47 Patton tank, but the automotive aspects were reversed. The engine was mounted in the front and drove through a front-drive sprocket. The driver's cupola is visible on the front left of the turret, and spare track blocks were stored on the turret front. Because the driver's seat was in the turret, a special seat was used to keep the driver facing forward, independent of the turret facing.

The M55 was used during the Vietnam War, and subsequently withdrawn from service in the US military.


1. http://www.globalsecurity.org/military/systems/ground/m55-8.htm

2. http://www.globalsecurity.org/military/systems/ground/m55-8-specs.htm

3. http://www.battletanks.com/m55.htm

4. http://afvdb.50megs.com/usa/8insphm55.html