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United States' M12 Gun Motor Carriage
Nickname: door knocker6

M12
United States' M12 Gun Motor Carriage
M12
At Battle of Bulge
United States' M12 Gun Motor Carriage
M12
In Germany 1945.
United States' M12 Gun Motor Carriage
M12
United States' M12 Gun Motor Carriage
M12
United States' M12 Gun Motor Carriage
Aberdeen Tank Museum
M12
   

Design

The Chief of Ordnance ordered a pilot model to have a 155 mm M1918M1 gun put onto a M3 medium chassis.1,5 This was designated the T6 and work began on it in June 1941.1,5

Engine

The engine was located in the front of the M12.

Crew

The vehicle commander and driver sat in a compartment at the front of the M12.6

The driver and assistant driver had direct and indirect vision. In the M12 there were seats for 4 other crewmen. There was also a hinged platform for the crew for firing.

The M12 provided armor protection for the crew.

Main Armament

The 155 mm M1918 was formerly a French gun that was used as towed artillery in World War I.6 After World War I they were placed into storage.6

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

Firing Spade

The M12 had a spade at the rear to help stabilize against the recoil of the gun.1 This could be raised when moving.

Prototype

The T6 prototype was manufactured by Rock Island Arsenal. Pressed Steel Car Company fitted French M1917 or US made M1918 guns.1

The T6 prototype started testing at the Aberdeen Proving Ground in February 1942.1,5 It had some modification done and was sent to Fort Bragg for the Field Artillery Board to test.5 The T6 proved acceptable, except to the Army Ground Forces, who felt towed artillery was good enough.1,6

During tests the T6 was fired, moved six miles, and then fired again.5 This took a total of 35 minutes to complete.5 A tractor towed 155 mm gun required three hours to do the same thing.5 The Ordnance Board ordered 50 initially, which was increased to 100.1,5

Production

Initial production of 100 of the M12 and M30 were completed in March 1943 by Pressed Steel Car Company.5 These were stored or used for training.5

When the Normandy landings was getting closer it was decided to remanufacture them.5 Baldwin Locomotive Works rebuilt 74 of them by May 1944 with the M4 chassis.1,5

Variants

Usage

Eventually 74 were sent to Europe in June 1944.5,6 They were used in the taking of Cologne5 and in busting the bunkers in the Siegfried Line1.

Used in Italy, France, and Germany.4

    M12 Gun Motor Carriage M30 Cargo Carrier
Crew   Commander, driver, gun crew (4)2,5
54, 61,2,5,6
 
Physical Characteristics      
Weight   58,000 lb2,5
26.3 tons1, 27.1 tons4, 29 tons6
26,762 kg1, 29,464 kg6
47,000 lb2,5
Length w/gun 22' 1" 22.1'4, 22' 1"5,6, 22' 3"1,2
6.67 m1, 6.73 m6
19' 10"2,5
Length w/o gun      
Height 8' 10" 8.8'4, 8' 10"2,5,6, 9' 6"1
2.69 m6, 2.88 m1
10'2,5
Width 8' 9" 8'4, 8' 9"1,2,5,6
2.67 m1,6
 
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 M1917 155 mm M19171  
OR 155 mm M1918A1 155 mm M1917A14  
OR 155 mm M1918M1 155 mm M19181  
OR   155 mm M1918M12,5,6  
Secondary      
MG   1: 0.5" Browning MG6
1: 12.7 mm Browning MG6
 
MG - anti aircraft     .50 cal Browning2,5
Side arms 5: .30 cal Carbines
Grenades
   
Quantity      
Main   64, 101,2,5,6 402,5,6
Secondary      
MG 1,000   1,0002,5
Side arms
22
   
Armor Thickness (mm) (Actual thickness at horizontal) 506
Front: 1"4
Side: 0.4"4
 
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-9752,5,6
Wright4
Continental R-9752
Bore / stroke      
Cooling   Air4  
Cylinders   R-94
Radial6
 
Capacity      
Net HP   3535,6, 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)   Gasoline4,5, Petrol6  
Octane      
Quantity   200 gallons4  
Road consumption   0.6 mpg4  
Cross country consumption      
Performance      
Traverse   14° left, 14° right2,5  
Max speed 24 mph 21 mph4, 24 mph1,2,5,6
38 kph1, 39 kph6
24 mph2
Cross country speed 12 mph 5-21 mph4, 12 mph2,5 12 mph2
Road radius 140 miles 120 miles4, 140 miles1,2,5,6
225 km6
140 miles2
Cross country radius      
Turning radius 35'    
Elevation limits   -5° to +30°2,5  
Fording depth 3' 3'2,4,5 3'2
Trench crossing 7' 6" 6'4, 7' 6"2,5 7' 6"2
Vertical obstacle 2' 18"4, 2'2,5 2'2
Climbing ability   22° (40%) slope4  
Suspension (Type) Vertical volute Vertical volute2,4,5 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"2,5 16.5"2
Diameter      
Number of links   794  
Pitch   6"4  
Tire tread      
Track centers/tread 6' 11" 6' 11"2,5, 6.95'4 6' 11"2

Sources:

  1. 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
  2. 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
  3. -
  4. Tank Data, Aberdeen Proving Grounds Series, 1968?
  5. Profile: AFV Weapons 26: Hellcat, Long Tom and Priest and Complete Check List of all U.S. World War II Self-Propelled Weapons, Colonel Robert J. Icks, 1971
  6. World Encyclopedia of Armored Fighting Vehicles, Jack Livesey, 2006
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