M4 Mortar Carrier:
Aberdeen Tank Museum
Standardized in October 1940. Classified as Limited Standard in December 1942.
Based on M3 chassis. Carried gun and ammo. Mortar had to be removed for firing. Was sometimes fired from inside of vehicle in emergencies. It faced the rear of the vehicle.1
M4A1 Mortar Carrier:
Standardized in December 1942, and classified as Limited Standard in July 1943.
Improved with reinforced floor and mounts for firing mortar from within half track. Had extra storage boxes at rear. Mortar fired to rear.1 Velocity of 700 ft/sec, range of 3,288 yards. Had a .30 cal Browning MG installed on the gun rail which went around the top. Also included a bazooka, M1 rifle, and a .45 cal submachine gun.
M21 Mortar Carrier:
Prototypes were manufactured by White Motor Co.
Had traversing mount and mortar fired forward.1 Traverse of 30° each way and elevation 40° to 80°. Pedestal mount in rear for .50 cal MG. Mortar could be removed for firing. A 2-way radio was also installed.
| M4 Mortar Carrier, M4A1 Mortar Carrier, M21 Mortar Carrier | |
|---|---|
| Crew | 61 |
| Physical Characteristics | |
| Weight | 17,325 lb1, 18,500 lb |
| Length w/gun | 19' 6.75"1, 20' 9 5/8" |
| Length w/o gun | |
| Height | 7' 5"1 |
| Width | 6' 5.25"1, 7' 3.5" |
| Width over tracks | |
| Ground clearance | 11 3/16"1 |
| Ground contact length | 46.75", 60"1 |
| Ground pressure | |
| Turret ring diameter | |
| Armament | |
| Main | 81 mm Mortar M11 |
| Secondary | |
| MG | M2 .50 cal MG .30 cal M1919A4 Browning MG1 |
| Side arms | M3 .50 cal MG Tripod mount .45 Submachine Gun M1 Rocket Launcher Grenades Mines |
| Quantity | |
| Main | 97, 1121 |
| Secondary | |
| MG | 400, 12,0001 |
| Side arms | 600 6 12 12 |
| Armor Thickness (mm) | |
| Hull Front, Upper | 0.5"@0°1, 12.72 |
| Hull Front, Lower | |
| Hull Sides, Upper | 0.25"@0°1 |
| Hull Sides, Lower | |
| Hull Rear | 0.25"@0°1 |
| Hull Top | |
| Hull Bottom | 6.35 |
| Turret Front | |
| Turret Sides | |
| Turret Rear | |
| Turret Top | |
| Engine (Make / Model) | White 160AX1 |
| Bore / stroke | |
| Cooling | Water1 |
| Cylinders | 61 |
| Capacity | |
| Net HP | 1471 |
| Power to weight ratio | |
| Compression ratio | |
| Transmission (Type) | Double range transfer case1 4 forward, 1 reverse1 |
| Steering | Front wheels, Ross steering gear1 |
| Steering ratio | |
| Starter | |
| Electrical system | |
| Ignition | |
| Fuel (Type) | Gasoline1 |
| Octane | |
| Quantity | 60 gallons1 |
| Road consumption | 3.3 mpg1 |
| Cross country consumption | |
| Performance | |
| Traverse | 60° to front |
| Max speed | 45 mph1 |
| Cross country speed | |
| Road radius | 180-215 miles, 200 miles1 |
| Cross country radius | |
| Turning radius | 30'1 |
| Elevation limits | +40° to +85° |
| Fording depth | 2' 8"1 |
| Trench crossing | |
| Vertical obstacle | 1'1 |
| Climbing ability | 30° slope1 |
| Suspension (Type) | Front wheels: Semi elliptic springs1 Rear tracks: Vertical volute springing1 |
| Wheels each side | Dual wheeled, 4-wheel bogie1 |
| Return rollers each side | 11 |
| Tracks (Type) | Endless band1 |
| Length | |
| Width | 12"1 |
| Diameter | |
| Number of links | |
| Pitch | 4"1 |
| Tire tread | |
| Track centers/tread | 63 13/16"1 |
| Tire size | 8.25 x 201 |
| Wheel base | 135.5"1 |
| Wheel centers | 64.5"1 |
| Production | M4: 1942- : 572 1941: White Motor Co.1 M4A1: White 1943 - : 600 M21: 110 |
Sources:
- Tank Data 2, Aberdeen Proving Grounds Series, E. J. Hoffschmidt and W. H. Tantum IV, 1969
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