| M3 gun motor carriage | |
|---|---|
 An M3 gun motor carriage manned by African-American soldiers. | |
| Type | Tank destroyer |
| Place of origin | United States |
| Production history | |
| Designer | Ordnance Department |
| Designed | 1940–41 |
| Manufacturer | Autocar Company |
| Produced | August–September 1941 February 1942 – April 1943 |
| No. built | 2,202 |
| Specifications | |
| Mass | 20,000 lb (9.1 t) |
| Length | 20.46 ft (6.24 m) |
| Width | 7.29 ft (2.22 m) |
| Height | 8.17 ft (2.49 m) (including gun shield) |
| Crew | 5 (commander, gunner, two loaders, and a driver) |
| Elevation |
|
| Traverse |
|
| Armor | 0.25–0.625 in (6.4–15.9 mm) |
Main armament | 1 × 75 mm (3.0 in) M1897 gun 59 rounds |
| Engine | White 160AX, 386 in3 (6,330 cc), 6-cylinder, compression ratio: 6.44:1 147 hp (110 kW) |
| Power/weight | 14.7 hp/ton |
| Transmission | Constant mesh |
| Suspension | Semi-ellipitical longitudinal leaf spring for wheels and vertical volute springs for tracks |
| Ground clearance | 11.2 in (280 mm) |
| Fuel capacity | 60 US gal (230 L) |
Operational range | 150 mi (240 km) |
| Maximum speed | 47 mph (75 km/h) |
The M3 gun motor carriage (M3 GMC) was a United States Army tank destroyer equipped with a 75 mm M1897A4 gun, which was built by the Autocar Company during World War II.
After observing the new and often decisive use of armored vehicles on both sides during the French campaign of 1940, the US Army decided that it required a 75 mm self-propelled gun, based on the chassis of the M3 half-track. This was initially known as the T12. However, after the addition of features such as the gun shield from the M2A3 (a carriage for the M1897A4), the new vehicle entered production under the name M3 gun motor carriage (or M3 GMC). Because the number of M2A3 gun shields available was insufficient for the M3 GMC order, a new gun shield was designed. Variants featuring the new shield were designated M3A1 GMC.
The T12/M3 first served in the Philippines Campaign in 1942 with the Provisional Field Artillery Brigade in the anti-tank and the fire-support role. It then served in North Africa in tank destroyer battalions. It was used ineffectively in the Battle of Kasserine Pass and several other engagements, but was used with success in the Battle of El Guettar. It also served in the Allied invasion of Sicily, but was eventually superseded by the M10 tank destroyer. A total of 2,203 were produced, of which 1,361 were converted back into M3A1 half-tracks.
The M3 GMC also served in the Pacific theater, starting with the Battle of Saipan. It proved effective against the Japanese Type 95 Ha-Go and Type 97 Chi-Ha tanks. It later served in the Battle of Okinawa, the Battle of Peleliu and many other island battles.