After considering the German strategy used in its conquer of the Low Countries and France during the 1940 campaigns, the United States Army focused on a new mobile tank destroyer as a counter to future combat with the European power. As expediency was key, it was decided that the M3 Half-Track personnel carrier proved suitable for the carrying of an anti-tank weapon - namely the 75mm M1897A4 field gun. The M1897A4 was nothing more than an American copy of the excellent French Army turn-of-the-century Canon de 75 modele 1897 regimental field gun, a weapon system eventually adopted by dozens of players including many in Europe. The gun supported an Armor-Piercing (AP) projectile as well as a standard U.S. Army High-Explosive (HE) shell, allowing it to accomplish multiple duties for the service.
The resulting vehicle became the 20,000lb "75mm Gun Motor Carriage M3". It retained the same form as the original M3 vehicles with a length over 20 feet, a width of 7 feet and a height of 8 feet with the gun mounted. The crew numbered five and included the driver, commander, gunner and two ammunition handlers for which there were 59 x 75mm projectiles carried aboard. Power was through a White 160AX gasoline-fueled engine of 142.5 horsepower with the vehicle reaching speeds of 43 miles per hour on roads and up to 200 miles in driving range. The hull was suspended atop a semi-elliptic volute spring suspension system for some comfort in going off-road. The driver sat conventionally at front left with the gunnery crew to reside in the rear, open-air section of the hull superstructure. Protection ranged from 6mm to 16mm in armor thickness, enough to cover small arms fire, though the gunnery crew was largely exposed. Self-defense was simply through personal weapons - 4 x M1 Carbines and 1 x Garand rifle were carried by the crew.
Other physical changes from the M3 design included a new, downward-folding windshield that was further notched to allow the gun tube to rest on it when in travel mode. Fuel tanks were moved to the back of the crew compartment which allowed ammunition storage to be added in a floor compartment.
Testing of the vehicle produced the T12 pilot model, a design headed by Major Robert Icks. Work began in June of 1941 months ahead of the official American declaration of war (December 1941). By October, the vehicle had been put through its paces and adopted in full as the 75mm GMC M3. From there, Autocar produced the first 86 of some 2,200 vehicles of which 170 or so were shipped to the British Army and used as the 75mm SP, Autocar (this in early 1943). The French and Philippines armies also held a stock of limited M3 GMCs from 1944 to 1945 and beyond.
First actions of M3s saw them delivered to the Philippines Front to content with the Japanese invasion. However, the campaign proved a failure for the Allies and those systems not lost in combat were taken over by the Japanese victors where ammunition supplies allowed it. The vehicles were then part of the North African campaign to remove the Axis presence there, seeing action in Tunisia (November 1942 - May 1943), Kasserine Pass (February 1943) and elsewhere in the theater throughout 1942-1943. Then came the retaking of Sicily in 1943 (July-August 1943) but by this time the vehicle was giving way to both combat attrition (losses) and the arrival of the M10 Gun Motor Carriage line - the "Wolverine" as the British named it. The appearance of heavier German armor did not help its cause for the 75mm was really only proven against light and early-war medium tank classes.
In 1944, the M3 GMC was officially declared obsolete by the U.S. Army with its replacements now well-entrenched. This did not stop its usage in the hands of the United States Marine Corps who still valued its 75mm gun and vehicle mobility against the light Japanese tanks during the Saipan (June-July 1944), Peleliu (September-November 1944) and Okinawa (April-June 1944) campaigns that followed. Its other valuable quality lay in used as an anti-fortification and anti-infantry weapon thanks to its HE shell power. By the end of the war, the USMC had too graduated to a newer vehicle - this becoming use of the 105mm M7 Priest models.
Some M3 GMCs soldiered on in the post-war years, particularly with the Philippine Army. Some were to see combat in the upcoming Korean War (1950-1953) before their time was to finally run out.
Beyond the initial M3 production model was the M3A1 which utilized different mounting hardware for its 75mm gun system. Despite the manufacture total of 2,200 vehicles, 1,360 of these gun carriers were eventually converted back to their traditional half-track forms as they were needed in greater numbers to move the masses of Allied troops. This left about 840 or so M3 GMCs in actual circulation throughout the war.
Manufacturing State Factories - USA
Production 2,200 Units
France; Imperial Japan; Philippines; United Kingdom; United States
- Anti-Tank / Anti-Armor
- Fire Support / Assault / Breaching
20.51 ft (6.25 m)
7.05 ft (2.15 m)
8.04 ft (2.45 m)
10 tons (9,100 kg; 20,062 lb)
(Showcased structural values pertain to the M3 Gun Motor Carriage (75mm) production model)
1 x White 160AX gasoline engine of 142.5 horsepower.
(Showcased powerplant information pertains to the M3 Gun Motor Carriage (75mm) production model)
43 mph (70 kph)
199 miles (320 km)
(Showcased performance values pertain to the M3 Gun Motor Carriage (75mm) production model; Compare this entry against any other in our database)
1 x 75mm M1897A4 gun
Ammunition: 59 x 75mm projectiles
(Showcased armament details pertain to the M3 Gun Motor Carriage (75mm) production model)
T12 - Experimental Vehicle Designation
75mm Gun Motor Carriage M3 - Formal US Army designation.
75mm Gun Motor Carriage M3A1 - Revised mounting hardware for 75mm gun system.
75mm SP, Autocar - British Army Designation; 170 examples.
The "Military Factory" name and MilitaryFactory.com logo are registered ® U.S. trademarks protected by all applicable domestic and international intellectual property laws. All written content, illustrations, and photography are unique to this website (unless where indicated) and not for reuse/reproduction in any form. Material presented throughout this website is for historical and entertainment value only and should not to be construed as usable for hardware restoration, maintenance, or general operation. We do not sell any of the items showcased on this site. Please direct all other inquiries to militaryfactory AT gmail.com.
Part of a network of sites that includes GlobalFirepower, a data-driven property used in ranking the top military powers of the world and WDMMA.org, the World Directory of Modern Military Aircraft.