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United States' M4, M4A1, M21 81 mm Mortar Carrier


M4 81 mm Mortar Carrier:
United States' M4 81 mm Mortar Carrier
Aberdeen Tank Museum


  • M4: 572
    • Production: 1941, 1942 - ?
    • Manufacturer: White Motor Co.
  • M4A1: 600
    • Production: 1943
    • Manufacturer: White
  • M21: 110


  • M4 Mortar Carrier: 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.
  • 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. 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. 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 6
Physical Characteristics  
Weight 17,325 lb, 18,500 lb
Length 19' 6.75", 20' 9 5/8"
Height 7' 5"
Width 6' 5.25", 7' 3.5"
Width over tracks  
Ground clearance 11 3/16"
Ground contact length 46.75", 60"
Ground pressure  
Turret ring diameter  
Main 81 mm Mortar M1
MG M2 .50 cal MG
.30 cal M1919A4 Browning MG
Side arms M3 .50 cal MG Tripod mount
.45 Submachine Gun
M1 Rocket Launcher
Main 97, 112
MG 400, 12,000
Side arms
Armor Thickness (mm)  
Hull Front, Upper 0.5"@0°, 12.72
Hull Front, Lower  
Hull Sides, Upper 0.25"@0°
Hull Sides, Lower  
Hull Rear 0.25"@0°
Hull Top  
Hull Bottom 6.35
Turret Front  
Turret Sides  
Turret Rear  
Turret Top  
Engine (Make / Model) White 160AX
Bore / stroke  
Cooling Water
Cylinders 6
Net HP 147
Power to weight ratio  
Compression ratio  
Transmission (Type) Double range transfer case
4 forward, 1 reverse
Steering Front wheels, Ross steering gear
Steering ratio  
Electrical system  
Fuel (Type) Gasoline
Quantity 60 gallons
Road consumption 3.3 mpg
Cross country consumption  
Traverse 60° to front
Speed - Road 45 mph
Speed - Cross Country  
Range - Road 180-215 miles, 200 miles
Range - Cross Country  
Turning radius 30'
Elevation limits +40° to +85°
Fording depth 2' 8"
Trench crossing  
Vertical obstacle 1'
Climbing ability 30° slope
Suspension (Type) Front wheels: Semi elliptic springs
Rear tracks: Vertical volute springing
Wheels each side Dual wheeled, 4-wheel bogie
Return rollers each side 1
Tracks (Type) Endless band
Width 12"
Number of links  
Pitch 4"
Tire tread  
Track centers/tread 63 13/16"
Tire size 8.25 x 20
Wheel base 135.5"
Wheel centers 64.5"


  1. Tank Data 2, Aberdeen Proving Grounds Series, E. J. Hoffschmidt and W. H. Tantum IV, 1969
20th Century American Military History Crucial Site