81mm Mortar Carrier M211-9

M21: General
Date of first acceptance January 1944 Total acceptances 110
Manufacturer White Motor Co. Crew 6 men
M21: Dimensions
Combat weight 20,000lbs
Height 89"
Length with winch 244.875"
Width over mine racks 87.5"
Front tread 64.5"
Rear tread 63.8"
Wheelbase 135.5"
Ground clearance 11.2"
Ground pressure, tires 29.4psi
M21: Armament
Type Mount Ammunition Traverse Elevation
81mm Mortar M1 Mount M1 97 rounds 60°
(30° left and right;
+85° to +40°
.50cal M2HB MG Flexible on pedestal mount 7115438 400 rounds 360°
M21: Armor
Rolled face-hardened steel
Location Thickness Angle from vertical
Radiator louvres .25"
Windshield cover .50"
Sides .25"
Rear .25"
Hood top .25"
M21: Automotive
Engine White 160AX; 6 cylinder, 4 cycle, in-line gasoline
Horsepower Net: 147@3000rpm Torque Net: 325 ft-lb@1200rpm Fuel capacity 60gal
Transmission Spicer 3461 constant mesh, 4 speeds forward, 1 reverse
Steering Steering wheel
Brakes Hydraulic (Hydrovac)
M21: Suspension
Type Road wheels Track return rollers
Front: Semi-elliptic longitudinal leaf spring
Rear: Vertical volute spring
Front: Steel ventilated disc
Rear: 1 bogie/track;
4 dual/bogie
1 dual/track
Drive sprockets Idlers Shock absorbers
18-tooth front drive Spring-loaded at rear of track On front wheels
M21: Track
Center guide band type
Width 12"
Pitch 4"
Pitches/track 58 Track ground contact length 46.75"
M21: Performance
Max level road speed 45mph
Max grade 60%
Max vertical obstacle 12"
Min turning diameter 59'
Max fording depth 32"
Cruising range ~200mi, roads
~320km, roads

The M21 mortar carrier was based on the half-track personnel carrier M3 and was similar to the M4 mortar carrier. In the M21, however, the mortar was fired to the front, and so the .50cal MG was positioned in the very rear of the vehicle, just in front of the rear door. The M21 also had rod-type stowage racks on the sides of the vehicle, which resembled ladders in construction. The top rod was used to secure the passenger compartment's canvas cover, and the bottom rod was used to secure stowage. The machine gun pedestal mount 7115438 was similar to the pedestal mount M25 found in the M3 half-track.

Home       Vehicle list       Top



  1. TM 9-710 Basic Half-Track Vehicles (White, Autocar, and Diamond T). Washington, DC: War Department, 23 February 1944.
  2. TM 9-710/TO 19-75A-77 Half-track Vehicles Car M2A1; Personnel Carrier M3 and M3A1; 81-mm Mortar Carrier M4, M4A1, and M21; Combination Gun Motor Carriage M15A1; and Multiple Gun Motor Carriage M16 and M16A1. Washington, DC: Departments of the Army and the Air Force, 8 May 1953.
  3. Hunnicutt, R.P. Half-Track: A History of American Semi-tracked Vehicles. Navato, CA: Presidio Press, 2001. Reprinted from Half-Track, R.P. Hunnicutt ©2001, available from Presidio Press, 505B San Martin Drive, Suite 160, Navato, CA 94945.
  4. 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.
  5. TM 9-2800 Standard Military Motor Vehicles. Washington, DC: War Dept., 1 Sep 1943.
  6. Crismon, Fred W. U.S. Military Tracked Vehicles. Osceola, WI: Motorbooks International, 1992.
  7. Chamberlain, Peter, and Chris Ellis. British and American Tanks of World War Two. Frome, England: Cassell & Co., 2000.
  8. Hogg, Ian V. The Greenhill Armoured Fighting Vehicles Data Book. London: Greenhill Books, 2000.
  9. Siemers, Cary. "USA's Half Track Gun Motor/Mortar Carriages." World War II Tanks & Vehicles and Advanced Squad Leader. 4 Jul 2001. 13 Aug 2001 <http://www.siemers.com/wwii/USA/GunMotorCarriage.htm>.

Last updated 5 Feb 2022.
Questions? Comments? Corrections? Email me
© Copyright 2001-22 Chris Conners