4.2" Mortar Motor Carriage M21-3

M2: General
Manufacturer White Motor Co. Total acceptances 6
Crew 5 men
M2: Dimensions
Weight, net, equipped 7,670lbs
3480kg
Height 81"
210cm
Length 202.50"
514.35cm
Width 80.37"
204.1cm
Front tread 63.75"
28.92cm
Rear tread 63.75"
28.92cm
Wheelbase 131"
333cm
Ground clearance 9.75"
24.8cm
Ground pressure 57psi
4.0kg/cm²
M2: Armament
Type Mount Traverse Elevation
4.2" Chemical Mortar M1A1 Mount in rear compartment Manual +45° to +60°
(manual)
.30cal M1919A4 MG Flexible on pedestal mount T34 360°
(manual)
Manual
M2: Armor
Assembly
Bolting
Location Thickness
Windshield .50"
1.3cm
Other surfaces .25"
.64cm
M2: Automotive
Engine Hercules JXD; 6 cylinder, 4 cycle, in-line gasoline
Horsepower 95@3000rpm Torque 224 ft-lb@1100rpm Fuel capacity 26.5gal
100L
Transmission Clark Equipment Co. Model 230-F combination sliding and constant mesh, 4 speeds forward, 1 reverse
Steering Ross Gear and Tool Co. Type 660 cam and lever type, steering wheel
Brakes Hydraulic, internal expanding
M2: Suspension
Type Road wheels Shock absorbers
Semi-elliptic leaf spring 2/side On each wheel
M2: Performance
Max level road speed 55mph
89kph
Min turning diameter 29.25'
8.915m
Angle of approach 37° Angle of departure 35°
Max fording depth 22.50"
57.15cm

The 4.2" mortar motor carriage M2 was based on the scout car M3. The machine gun skate rail was removed from the rear compartment, and the mortar mount was emplaced centrally. The mortar could be detached from the vehicle for firing. When dismounted, elevation from 45° to 60° was achievable, and when fired while attached to the carrier, 60° of elevation was possible. An ammunition rack for the mortar was installed behind the 3-man driver's compartment, and two seats were retained in the rear for the gun crew. The rear seats needed to be removed to access the mortar ammunition. The machine gun was installed on a pedestal mount on the passenger running board behind the front fender.

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References

  1. Hunnicutt, R.P. Armored Car: A History of American Wheeled Combat Vehicles. Novato, CA: Presidio Press, 2002. Reprinted from Armored Car, R.P. Hunnicutt ©2002, available from Presidio Press, 505B San Martin Drive, Suite 160, Novato, CA 94945.
  2. TM 9-705 Scout Cars, M3, M3A1, and 4.2 Mortar Motor Carriage, M2. Washington, DC: War Department, 19 February 1941.
  3. Doyle, David. U.S. Half-tracks: The Development and Deployment of the U.S. Army's Half-track Based Multiple Gun Motor Carriages and Gun Motor Carriages, Part two. Ed. Pat Stansell. Delray Beach, FL: The Ampersand Publishing Group, Inc., 2016.

Last updated 7 Oct 2021.
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