M-3 Gun Motor Carriage

The M3 Gun Motor Carriage (GMC), known as T-12 pre-standardization, was a mobile tank-destroyer based on the White M3 Halftrack with a mounted M1897 or M2 75mm field gun. The gun and its shield were mounted in the cargo space of the halftrack, positioned to fire forward over the drivers compartment. The windshield area and windshield cover were modified to enable the gun to project to the front.

The M3 Gun Motor Carriage was standardized in November 1941 and was used in the defense of the Philippines as well as in the Operation Torch invasion of North Africa in 1942. The lightweight 75mm gun did well against thinly armored Japanese tanks, but German armor was much tougher and the 75mm cannon fire did not penetrate. The M3 GMC was used until mid-1944 after which it was considered obsolete.

This vehicle was also called M3 75mm Self-propelled Mount (SPM) by the special weapons companies of the USMC.

For a time during World War II the M3 GMC was used as the insignia for Tank Destroyer Forces. AR 600-35, dated 13 March 1943, specified the design was a "75-mm gun, motor carriage M3, in gold color metal." The insignia was rescinded by Change 2, AR 600-35, dated 28 November 1944.

Tank Destroyer Forces Insignia
Tank Destroyer Forces Insignia

Today in WW II: 11 Nov 1940 55 Polish intellectuals murdered in Dachau concentration camp [near Munich], the first of many mass executions there.  More 
11 Nov 1940 Operation SWORDFISH: Raid on Taranto, Italy, the British Royal Navy's first all-aircraft naval attack, launching obsolete canvas planes from an aircraft carrier [11-12 Nov].
11 Nov 1942 Triggered by Operation Torch in N. Africa, Germans take control of all of Vichy France north of the Riviera.
11 Nov 1942 Allies capture Casablanca, Morocco during Operation Torch.
11 Nov 1942 In the aftermath of Operation Torch, Germany and Vichy France begin negotiations on the fate of the French fleet at Touson.
Visit the Olive-Drab.com World War II Timeline for day-by-day events 1939-1945! See also WW2 Books.

M-3 Gun Motor Carriage (GMC) with 75mm Howitzer Specifications

Crew 5
Weight 10 tons
Height 8 ft, 2 in.
Width 7 ft, 1 in.
Length 20 ft, 6 in.
Engine White 160AX 6 cyl. gasoline
Horsepower 128 bhp
Road Speed 45 mph
Range 200 mi.

The M-3 GMC carried 59 rounds of 75mm ammunition in the cargo area with the gun. The M3 GMC was used by the U.S. Army in North Africa and Europe as well as by the USMC in the Pacific.

Thanks to Bukvoed for help with this page and proper ID of the M3 GMC.

Recommended Book About the M3 Gun Motor Carriage

Almost invisible in the thick jungle vegetation, an M3 GMC supports Marine operations on Hill 660, Cape Gloucester, New Britain, December 1943 - January 1944.  The barrel of the 75mm gun points to the left, just left of center
Almost invisible in the thick jungle vegetation, an M3 GMC supports Marine operations on Hill 660, Cape Gloucester, New Britain, December 1943 - January 1944. The barrel of the 75mm gun points to the left, just left of center.

M3 75mm Gun Motor Carriage halftracks, airbase security, North Africa during WW II
M3 75mm Gun Motor Carriage halftracks, airbase security, North Africa during WW II.

M-3 75mm Gun Motor Carriage, Special Weapons Company, 2nd Marine Division, Tinian, 30 July 1944
M3 75mm Gun Motor Carriage, Special Weapons Company, 2nd Marine Division, Tinian, 30 July 1944.

M-3 75mm Gun Motor Carriage, Italy, 1945.  Second unit is to the right
M3 75mm Gun Motor Carriage, Italy, 1945. Second unit is to the right.