M12 Gun Motor Carriage:
Aberdeen Tank Museum
At Battle of Bulge
In Germany 1945.
The Chief of Ordnance ordered a pilot model to have a 155 mm M1918M1 gun put onto a M3 medium chassis.1 This was designated the T6 and work began on it in June 1941.1 It was tested in February 1942.1 It proved acceptable except to the Army Ground Forces who felt towed artillery was good enough.1 The Ordnance Board ordered 50 initially, which was increased to 100.1
Prototype was manufactured by Rock Island Aresenal. Pressed Steel Car Company fitted French M1917 or US made M1918 guns.1
M1918M1, M1917A1, or M1917 155 mm gun mounted on a 155 mm Gun Mount, M4, on a modified M3 medium tank chassis. The engine was moved forward.
The 155 mm gun fired a 95 lb shell at a muzzle velocity of 2,380'/sec and a range of 18,000 yards.4
There was a spade at the rear to help stabilize against the recoil of the gun.1 This could be raised when moving. There is also a hinged platform for the crew for firing.
The driver and assistant driver have direct and indirect vision. There are seats for 4 other crewmen.
Initially only used for training, but with the invasion of Europe to happen, it was decided to prepare them for combat.1 74 were upgraded by the Baldwin Locomotive Works to the M4 chassis.1
There was now armor protection for the crew as it was intended to be well behind the front lines and used as long range artillery.
Eventually 75 were sent to Europe. They were used in the taking of Cologne and in busting the bunkers in the Siegfried Line1.
Used in Italy, France, and Germany.4
M30:
Produced by Pressed Steel Car Company.
Cargo Carrier M30:
Identical to M12 except no gun. There was on M30 for each M12. The crew primarily traveled in the M30. There was a tailgate to help unload the ammunition. A ring mount for a .50 cal MG was installed in the rear.
| M12 | M30 | ||
|---|---|---|---|
| Crew | Commander, driver, gun crew (4)2 54, 61,2 |
||
| Physical Characteristics | |||
| Weight | 58,000 lb2 26.3 tons1, 26.4 tons3, 27.1 tons4 26,762 kg1 |
47,000 lb2 | |
| Length w/gun | 22' 1" | 22.1'4, 22' 3"1,2 6.67 m1, 6.73 m3 |
19' 10"2 |
| Length w/o gun | |||
| Height | 8' 10" | 8.8'4, 8' 10"2, 9' 6"1 2.88 m1, 2.69 m3 |
10'2 |
| Width | 8' 9" | 8' 9"1,2 8'4, 2.67 m1,3 |
|
| Width over tracks | |||
| Ground clearance | 17 1/8" | 16"4 | |
| Ground contact length | 14' 3" | 148"4 | |
| Ground pressure | 11.6 psi | 11.5 psi4 | |
| Turret ring diameter | |||
| Armament | |||
| Main | 155 mm M1918M1, M1918A1, or M1917 | 155 mm M1917 or M19181 155 mm M1918M12 155 mm M1917, M1917A1, OR M1918M13 155 mm M1917A14 |
|
| Secondary | |||
| MG | .50 cal Browning AA2 | ||
| Side arms | 5: .30 cal Carbines Grenades |
||
| Quantity | |||
| Main | 64, 101,2,3 | 40 (155 mm shells)2 | |
| Secondary | |||
| MG | 1,000 | 1,0002 | |
| Side arms | 22 |
||
| Armor Thickness (mm) | (Actual thickness at horizontal) | Front: 1"4, 503 Side: 0.4"4, 203 |
|
| Hull Front, Upper | 1.5-2" (3.5") | ||
| Hull Front, Lower | |||
| Hull Sides, Upper | 1" | ||
| Hull Sides, Lower | |||
| Hull Rear | 0.75" | ||
| Hull Top | 0.5" | ||
| Hull Bottom | 0.5-1" | ||
| Turret Front | Shield: 0.75" | ||
| Turret Sides | |||
| Turret Rear | |||
| Turret Top | |||
| Engine (Make / Model) | Continental R-975 C1 | Continental R-9752 Wright4 |
Continental R-9752 |
| Bore / stroke | |||
| Cooling | Air4 | ||
| Cylinders | R-94 | ||
| Capacity | |||
| Net HP | 3503, 400@2,400 rpm4 | ||
| Power to weight ratio | |||
| Compression ratio | |||
| Transmission (Type) | Syncromesh | Synchromesh4 5 forward, 1 reverse4 |
|
| Steering | Controlled differential4 | ||
| Steering ratio | |||
| Starter | Electric4 | ||
| Electrical system | 24-volt4 | ||
| Ignition | Magneto4 | ||
| Fuel (Type) | Gasoline4 | ||
| Octane | |||
| Quantity | 200 gallons4 | ||
| Road consumption | 0.6 mpg4 | ||
| Cross country consumption | |||
| Performance | |||
| Traverse | 14° left, 14° right2,3 | ||
| Max speed | 24 mph | 21 mph4, 24 mph1,2 38 kph1, 40 kph3 |
24 mph2 |
| Cross country speed | 12 mph | 5-21 mph4, 12 mph2 | 12 mph2 |
| Road radius | 140 miles | 120 miles4, 140 miles1,2 225 km |
140 miles2 |
| Cross country radius | |||
| Turning radius | 35' | ||
| Elevation limits | -5° to +30°2,3 | ||
| Fording depth | 3' | 3'2,4 | 3'2 |
| Trench crossing | 7' 6" | 6'4, 7' 6"2 | 7' 6"2 |
| Vertical obstacle | 2' | 18"4, 2'2 | 2'2 |
| Climbing ability | 22° (40%) slope4 | ||
| Suspension (Type) | Vertical volute | Vertical volute2,4 | Vertical volute.2 |
| Wheels each side | 3 x 2-wheeled bogies4 | ||
| Return rollers each side | 34 | ||
| Tracks (Type) | Rubber block, double pin4 | ||
| Length | |||
| Width | 16.5" | 16"4, 16.5"2 | 16.5"2 |
| Diameter | |||
| Number of links | 794 | ||
| Pitch | 6"4 | ||
| Tire tread | |||
| Track centers/tread | 6' 11" | 6' 11"2, 6.95'4 | 6' 11"2 |
| Production | 1944: 100 | Pressed Steel Car Co.4 |
Sources:
- The Encyclopedia of Tanks and Armored Fighting Vehicles - The Comprehensive Guide to Over 900 Armored Fighting Vehicles From 1915 to the Present Day, General Editor: Christopher F. Foss, 2002
- British and American Tanks of World War Two, The Complete Illustrated History of British, American, and Commonwealth Tanks 1933-1945, Peter Chamberlain and Chris Ellis, 1969
- Jane's World War II Tanks and Fighting Vehicles The Complete Guide, Leland Ness, 2002
- Tank Data, Aberdeen Proving Grounds Series, 1968?
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