75mm Gun Motor Carriage M31-12

M3: General
Date of first acceptance August 1941 Total acceptances 2202 M3 and M3A1
(1360 converted to M3A1 personnel carriers)
Manufacturer Autocar Co. Crew
5 men:
  • Gun commander in cab right
  • Gunner in rear left
  • Driver in cab left
  • Assistant gunner rear right
  • Loader in rear
M3: Dimensions
Combat weight 20,000lbs
Height over gun shield 98.6"
Length 245.5"
Gun overhang forward 0"
Width over side armor 77.25"
Fire height 81.9"
Front tread 64.5"
Rear tread 63.8"
Wheelbase 135.5"
Ground clearance 11.2"
M3: Armament
Type Mount Ammunition Traverse Elevation
75mm Gun M1897A4 Mount M3 59 rounds 40°
(19° left and 21° right;
+29° to -10°
M3: Armor
Rolled face-hardened steel
Location Thickness Angle from vertical
Gun shield front .625"
Gun shield sides .25"
Gun shield top .25"
Radiator louvres .25"
Windshield cover .50"
Sides .25"
Rear .25"
Hood top .25"
M3: 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
M3: 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 Adjustable fixed at rear of track On front wheels
M3: Track
Center guide band type
Width 12"
Pitch 4"
Pitches/track 58 Track ground contact length 46.75"
M3: 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 M3 75mm GMC was based on the M3 half-track, and essentially stuck a 75mm gun behind the driving compartment. A low, sloping gun shield was provided for the gun crew, and the armored windshield cover had a notch cut in the middle to allow room for the gun. The glass was removed from the windshield cover, and it folded down onto the hood instead of upwards as on the M3 half-track, since the GMC lacked a roof over the driving compartment. The fuel tanks were relocated to the rear, and stowage boxes were attached to the rear of the vehicle on either side of the rear door. The M3 gun mount consisted of the standard M2A3 gun carriage--less its wheels, axle, and equalizers--resting on a steel base. Modifications to the M3 half-track were also applied to the M3 GMCs.

Insufficient quantities of the M2A3 gun carriages used in the mount M3 forced the use of older M2A2 gun carriages in the 75mm GMC. The mount using the gun carriage M2A2 was designated M5, and the GMC using the gun mount M5 was standardized as M3A1. The M5 mount was mounted 3.75" (9.53cm) towards the rear of the vehicle compared to the M3 mount. Elevation and traverse with the M5 were -6.5° to +29°, and 21° right and left, respectively.

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  1. TM 9-710 Basic Half-Track Vehicles (White, Autocar, and Diamond T). Washington, DC: War Department, 23 February 1944.
  2. TM 9-306 75-mm Gun M1897A4 Mounted in Combat Vehicles. Washington, DC: War Department, 10 June 1943.
  3. TDS 105-11 Tank Destroyer Weapons, Chapter 11 75-mm Gun, M1897A4 on Motor Carriage, M3A1. Camp Hood, TX: Tank Destroyer School Weapons Dept., March 1943.
  4. 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.
  5. 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.
  6. Catalogue of Standard Ordnance Items, second edition 1944, volume I: Tank and Automotive. Washington, D.C.: Office of the Chief of Ordnance, Technical Division, 1 June 1945.
  7. Standard Nomenclature List G-102. 30 Sep 1943.
  8. Moran, Nicholas. Can Openers: The Development of American Anti-Tank Gun Motor Carriages. Brattleboro, VT: Echo Point Books & Media, 2017.
  9. Gill, Lonnie. Tank Destroyer Forces--WWII. Paducah, KY: Turner Publishing Co., 1992.
  10. Chamberlain, Peter, and Chris Ellis. British and American Tanks of World War Two. Frome, England: Cassell & Co., 2000.
  11. Hogg, Ian V. The Greenhill Armoured Fighting Vehicles Data Book. London: Greenhill Books, 2000.
  12. Siemers, Cary. "USA's Half Track Gun Motor/Mortar Carriages." World War II Tanks & Vehicles and Advanced Squad Leader. 4 Jul 2001. 8 Aug 2001 <http://www.siemers.com/wwii/USA/GunMotorCarriage.htm>.

Last updated 24 Oct 2016.
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© Copyright 2001-16 Chris Conners