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United States' M8 Howitzer Motor Carriage

Photos

M8 Howitzer Motor Carriage:
United States' M8 Howitzer Motor Carriage
Aberdeen Tank Museum

Design

The M8's hull was completely welded except for some of the front, top, and rear, which could be removed for maintenance.

Hull

To make room for the turret the front hatches for the driver had to be moved forward.

Engine

The M8 was powered by two Cadillac V8 engines.

Ammunition Trailer

As the M8 only carried 46 rounds, often an ammunition trailer was fitted.

Armament

The 75 mm gun fired a 18 lb HE shell at a muzzle velocity of 1,250'/sec. The .50 cal MG fired at 2,900'/sec.

Rate of fire for howitzer was 25 rounds/minute for a range of 9,610 yards.

Prototype

The prototype model was produced by Cadillac Motor Car Division of General Motors Corp on a M5 light tank chassis.

The T41 Howitzer Motor Carriage was a prototype mockup that was mounted in the center of a M5 Light Tank hull. The project was abandoned.

The next prototype was the T47, and it mounted a M2 or M3 75 mm Howitzer in a turret. A prototype was finished in April 1942. The T47 was tested at Aberdeen in early 1942. This was accepted and became the M8.

Production

  • Total: 1,778
    • Manufactured by: Cadillac Motor Car Co. (1942), GMC
    • Production: September 1942 - January 1944

Variants

  • T41 Howitzer Motor Carriage: Prototype. Howitzer mounted in center of hull.
  • T47 Howitzer Motor Carriage: Prototype. Howitzer mounted in turret.
  • M8 Howitzer Motor Carriage: Based on M5 chassis. Fitted with trailer hook for an ammo trailer.
  • M8A1 Howitzer Motor Carriage: Used M5A1 chassis.

Usage

First use was in Italy in late 1943. Used in France extensively, and supplied to the Free French. Also used in the Pacific by the Marines Corps.

Equipped HQ companies of medium tank battalions.

As the M7 became available in larger numbers the M8s were moved to reconnaissance units.

Specifications

  M8 Howitzer Motor Carriage
Crew 4
Physical Characteristics  
Weight 33,000 lb, 36,000 lb
15.446 tons, 15.45 tons
15,605 kg, 15,695 kg
Length 14' 3", 14' 6", 14' 6.75"
4.34 m, 4.41 m
Height 7' 6.5", 7' 7"
2.31 m, 2.32 m
Width 7' 4", 7' 4.25", 7' 5"
2.24 m, 2.26 m
Width over tracks  
Ground clearance 6.5", 16.5"
Ground contact length 120", 10' 1"
Ground pressure 11.6 psi, 11.83 psi
Turret ring diameter 54.5"
Armament  
Main 75 mm M2
75 mm M2 howitzer
M1A1 75 mm M2
75 mm Howitzer M3
OR M1A1 75 mm M3
Secondary  
MG 1: 12.7 mm (.50 cal) MG
1: 12.7 mm Browning MG
MG - anti aircraft 1: M2 .50 cal
1: .50 cal HBM2 MG
Side arms .45 cal submachine gun
M1 .30 Carbines
Grenades
Quantity  
Main 46
Secondary  
MG 400
Side arms 600
735
8
Armor Thickness (mm) 44
(Actual thickness at horizontal)
Hull Front, Upper 1.5"@0°, 1 1/8" (2.5")
Hull Front, Lower 1.75" (2.5")
Hull Sides, Upper 1.125"@0°, 1" (1 1/8")
Hull Sides, Lower  
Hull Rear 1"@0°
Hull Top 0.5"
Hull Bottom 3/8-0.5"
Turret Front 1.5"@0°
Turret Sides 1"@0°
Turret Rear 1"
Turret Top 3/8"
Engine (Make / Model) 2: Cadillac Series 42
Bore / stroke  
Cooling Water
Cylinders 2 x V-8
Capacity  
Net HP 110 each
220
Power to weight ratio  
Compression ratio  
Transmission (Type) Hydromatic
6 forward, 1 reverse
Steering Controlled differential
Steering ratio  
Starter  
Electrical system  
Ignition  
Fuel (Type) Gasoline, Gasoline
Octane  
Quantity 89 gallons
Road consumption 2 mpg
Cross country consumption  
Performance  
Traverse 360°
Manual
Speed - Road 35 mph, 36 mph, 45 mph
56 kph, 58 kph
Speed - Cross Country 24 mph
Range - Road 100 miles, 130 miles, 180 miles
161 km, 210 km
Range - Cross Country  
Turning radius  
Elevation limits +40° to -20°
Fording depth 2' 6", 3'
Trench crossing 5' 4", 5' 5"
Vertical obstacle 1' 6", 2'
Climbing ability 30° slope
Suspension (Type) Vertical volute
Vertical volute springing
Wheels each side 4
2 double wheel bogies
Return rollers each side 2
Tracks (Type) Steel or rubber with rubber bushed track pins
Length  
Width 11 5/8"
Diameter  
Number of links 67
Pitch 5.5"
Tire tread Rubber
Track centers/tread 6' 1.5", 73"

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. -
  3. Tank Data 2, Aberdeen Proving Grounds Series, E. J. Hoffschmidt and W. H. Tantum IV, 1969
  4. 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
  5. World Encyclopedia of Armored Fighting Vehicles, Jack Livesey, 2006
20th Century American Military History Crucial Site