M12 155mm – Procházka

Primary Role and Design

The M12 Gun Motor Carriage (GMC) was an American self-propelled artillery vehicle developed during World War II. It was designed to provide long-range heavy fire support that could keep pace with fast-moving armored divisions.

• Podvozek: The M12 was built on a modified and lengthened chassis of the obsolescent M3 Grant/Lee medium tank.
• Layout: The engine was moved forward to the center of the vehicle to accommodate the massive gun mount and recoil system at the rear.
• Gun Compartment: The gun crew and breech mechanism were located in a large, open-topped compartment at the back, offering minimal protection, in contrast to the heavily armored driver and commander positions at the front.

Armament and Support

The main weapon was a powerful, if vintage, piece of ordnance:

Specifikace	Detail
Main Armament	155 mm M1917 or M1918 gun (a US-produced version of the French Canon de 155 mm GPF from WWI).
Ammunition Capacity	Pouze 10 rounds of 155 mm ammunition could be carried on the M12 itself due to space constraints.
Recoil System	A large, hydraulically operated earth spade (or recoil shovel) at the rear was lowered into the ground before firing to absorb the immense recoil.
Support Vehicle	The M12 operated in tandem with the M30 Cargo Carrier (a virtually identical vehicle without the gun), which carried the remaining crew (six men) and up to 40 additional 155 mm rounds.

Service and Legacy

Only 100 M12s were manufactured between 1942 and 1943. Initially used for training, 74 vehicles were later refurbished and sent to Europe in 1944. They proved highly effective in the European Theater of Operations, particularly for:

• Heavy Indirect Fire: Providing deep-range artillery support.
• Direct Fire: Earning the nickname “Doorknocker” for its successful use in direct-fire mode against heavily fortified targets, especially German bunkers in the Siegfried Line, where the 155 mm shells could penetrate significant thicknesses of concrete.

The M12’s design—mounting a heavy gun rearward on a tracked chassis with an open fighting compartment and a recoil spade—established a template for future US self-propelled artillery, which was later improved upon by the M40 Gun Motor Carriage.