|155 mm Gun Motor Carriage M40|
M40 in the US Army Ordnance Museum.
|Place of origin||United States|
|Weight||36.3 metric tons (80,000 lb)|
|Length||9.1 m (29 ft 10 in)|
|Width||3.15 m (10 ft 4 in)|
|Height||2.7 m (8 ft 10 in)|
|Crew||8 (Commander, driver, 6 gun crew)|
|155 mm M2 gun|
|Engine||Wright (Continental) R975 EC2|
340 hp (253 kW)
|Suspension||HVSS (Horizontal Volute Spring Suspension)|
|170 km (106 mi)|
|Speed||38 km/h (24 mph) on road|
23 km/h (14 mph) off road
The 155 mm Gun Motor Carriage M40 was a US self-propelled artillery vehicle built on a widened and lengthened Medium Tank M4A3 chassis but with Continental engine and with HVSS (Horizontal Volute Spring Suspension) that was introduced at the end of the Second World War. Equipped with a 155 mm M2 gun, it was designed to replace the earlier M12 Gun Motor Carriage. Its prototype designation was the T83, but this was changed to the M40 in March 1945.
A single pilot vehicle was used in the European Theatre in 1945 by 991st Field Artillery Battalion, along with a related 8 inch Howitzer Motor Carriage T89 which was sometimes also equipped with a 155 mm barrel. A total of 311 out of a planned 600 were completed before the end of the war. From there it was deployed during the Korean War.
After World War II the M40 was used by the British Army, who designated it '155 mm SP, M40 and called it Cardinal in the tradition of using ecclesiastical names for SP artillery, such as Deacon, Priest, Bishop and Sexton.
A complete gun section consisted of one M40 GMC, one M4A1 high speed tractor towing an M23 ammunition trailer. each battery had 4 gun sections. the M4A1/M23 combo replaced the earlier M30 cargo carrier. 
The Army planned to use the same T38 chassis for a family of SP artillery:
- Cargo Carrier T30 - a few built before cancellation in December 1944 to make more chassis available for GMCs
- 8 inch Howitzer Motor Carriage M43 - 8 in (203 mm) HMC, standardized August 1945, 48 built
- 250 mm Mortar Motor Carriage T94 - 10 in (250 mm) MMC, began design Feb. 1945, one prototype completed in 1946
- 105 mm Howitzer Motor Carriage M7B1 - self-propelled 105 mm Howitzer Motor Carriage (HMC) based on the M4A3 Sherman chassis.
- 155 mm Gun Motor Carriage M12 - self-propelled 155 mm Gun Motor Carriage (GMC).
- Cargo Carrier M30 - an M12 with crew and ammunition space in lieu of the gun.
- one at United States Army Ordnance Museum
- one at the Imperial War Museum, Duxford (UK)
- one at Royal Artillery Museum, Woolwich (UK)
- one at the Technik Museum, Sinsheim (Germany)
- Two M40 GMCs – Arkansas National Guard Mus, Camp Robinson, Little Rock, AR (USA)
- one at City vehicle storage area, Charleston, AR (USA)
- one at the United States Army Field Artillery Museum, Fort Sill, Ok (USA)
- Hunnicutt - Sherman: A History of the American Medium Tank, p 353-355, 570.
- Hunnicutt, R. P. (1994). Sherman: A History of the American Medium Tank. Presidio Press. ISBN 0-89141-080-5.
- Ness, Leland (2002). Janes World War II Tanks and Fighting Vehicles. Harper Collins. ISBN 0-00-711228-9.
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