M12 Gun Motor Carriage
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|155mm Gun Motor Carriage M12|
M12 firing across the Moselle River in France, 1944.
|Place of origin||United States|
|Wars||World War II|
|Variants||Cargo Carrier M30|
|Length||6.73 m (22 ft 1 in)|
|Width||2.67 m (8 ft 9 in)|
|Height||2.70 m (8 ft 10 in)|
|Crew||6 (Commander, driver, (4x) gun crew)|
|155 mm M1917/18 M1 gun
|.50cal (12.7 mm) Browning M2 machine gun|
|Engine||Wright (Continental) R975 EC2
|Suspension||vertical volute spring|
|220 km (140 mi)|
|Speed||38 km/h (19 km/h off road)|
The M12 was built on the chassis of the M3 Lee tank; some sources claim that later M12s used the M4 Sherman chassis, but this might be a confusion with the M12's use of "Sherman-style" bogie trucks with trailing idlers.
It had an armored driver's compartment, but the gun crew were located in an open topped area at the back of the vehicle. It mounted a 155 mm gun M1917, M1917A1 or M1918 M1, depending upon availability, a weapon derived from the nearly identical French 155 mm GPF gun of World War I vintage. Limited storage space meant that only 10 projectiles and propellant charges could be carried on the vehicle.
An earth spade (similar to a bulldozer blade) at the rear was employed to absorb recoil. This layout—large gun mounted in an open mount at the rear, with a spade—was the pattern adopted for many years by other heavy self-propelled artillery.
Only 100 vehicles were built: 60 in 1942 and a further 40 in 1943.
Given the limited ammunition carried in the M12, a support vehicle based on the same chassis was produced as the Cargo Carrier M30. It was designed to transport the gun crew and additional ammunition.
In operational conditions, the M12 and M30 would serve in pairs.
During 1943, the vehicles were used for training or put into storage. Before the invasion of France, 74 M12s were upgraded in preparation for combat operations. They were employed successfully throughout the campaign in North-West Europe. Although designed primarily for indirect fire, during assaults on heavy fortifications, the M12s were sometimes employed in a direct-fire role.
In 1945, the M12 was complemented in Europe by the M40 Gun Motor Carriage, designed on a late-war M4 Sherman chassis. Postwar, the M12 was retired from service and replaced by the M40.
- The sole surviving M12 GMC is displayed at the Fort Sill museum , it was stored at the United States Army Ordnance Museum in Aberdeen, Maryland, USA, before being transferred to Fort Sill in November 2010.
- Leland Ness (2002) Janes World War II Tanks and Fighting Vehicles, Harper Collins, ISBN 0-00-711228-9
- Vehicle material
- TM 9-2300 military vehicles
- TM 9-751 operators
- TM 9-1750
- TM 9-1750B
- TM 9-1750D
- TM 9-1751
- SNL G158 parts catalog
- Gun material
- TM 9-2300 standard artillery and fire control material
- TM 9-345 155-mm M1918MI 
- TM 9-1345
- SNL D36