| M3 Gun Motor Carriage | |
|---|---|
 An M3 Gun Motor Carrier on display. | |
| Type | Tank destroyer |
| Place of origin |  United States |
| Service history | |
| In service | 1941 – 1945 |
| Used by |  United States United Kingdom |
| Wars | World War II |
| Production history | |
| Designer | Ordnance Department |
| Designed | 1940 – 1941 |
| Manufacturer | Autocar Company |
| Produced | August–September 1941 February 1942 – April 1943 |
| No. built | 2,202 (1,360 converted to M3A1 Half-track) |
| 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) (includinggun shield) |
| Crew | 5 men[1]
|
| Elevation |
|
| Traverse |
|
| Armor | 0.25–0.625 in (6.4–15.9 mm) |
Main armament | 1× 75 mm (3.0 in)M1897A4 gun (w/ 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 longitudinalleaf spring for wheels andvertical volute springs for tracks |
| Ground clearance | 11.2 in (280 mm) |
| Fuel capacity | 60 US gal (230 L)[1] |
Operational range | ~ 200 mi (320 km)[1] |
| Maximum speed | 47 mph (75 km/h) |
TheM3 Gun Motor Carriage (M3 GMC) was aUnited States Armytank destroyer equipped with a75 mm M1897A4 gun, which was built by theAutocar Company duringWorld War II.
The M3 GMC was 20.46 feet (6.24 m) long, 7.29 feet (2.22 m) wide, 8.17 feet (2.49 m) high (including thegun shield), and weighed 20,000 pounds (9.1 t). Its suspension consisted of semi-elliptical longitudinalleaf springs for the wheels andvertical volute springs for the tracks, while its transmission consisted of constant mesh. Its ground clearance was 11.2 inches (280 mm).[2][3]
It had aWhite 160AX 147 horsepower (110 kW), 386 cubic inch (6,330 cc),[4] 6-cylinder engine with a compression ratio of 6.44:1. It had a 150-mile (240 km) range,[5] 60 US gal (230 L) fuel tank, a speed of 47 mph (75 km/h), and a power to weight ratio of 14.7 hp per ton.
It was armed with one 75 mmM1897A4 with 59 rounds, had 0.25–0.625 in (6.4–15.9 mm) of armor, and a crew of five consisting of a commander, gunner, two loaders, and a driver. The M3 (with the M2A3 mount) could traverse 19° left and 21° right, elevate 29° and depress −10°. The M3A1 (using the M5 mount) could traverse 21° in both directions, but could only depress −6.5°.[2][3] Firing the M61 armor piercing round, the gun could penetrate up to 3 inches (76 mm) of armor at 1,000 yards (910 m).[6]
After thefall of France, the U.S. Army studied the reasons behind the effectiveness of theGerman campaign against the French and British forces. One aspect that was highlighted by this study was theuse of armored vehicles andself propelled artillery. However by 1941 there was little available in the U.S. Army's arsenal that could be used in such a role, the US Army decided that it required a 75 mmself-propelled gun. The Army had a number of M1897A5 guns, sufficient for the mass-production for such a weapon, and theM3 half-track was coming into production. After some debate, the Army decided to place M1897A5 guns on the M3 half-track chassis,[7] which was designated the T12 GMC. The M1897A5 gun was originally adapted for the M3 chassis by placing it in a welded box riveted to the chassis behind the driver's compartment. It was accepted by the Army on 31 October 1941.[8]
A batch of 36 T12s was used for testing, while another 50 were built and transported tothe Philippines.[9] The 36 T12s were improved in multiple ways. The improvements included the inclusion of a mount that raised the gun shield, the replacement of the original gun shield with a gun shield from theM2A3 (a carriage for the M1897A4), and the addition of a0.5 in (12.7 mm) M2 Browning machine gun, which was later removed. After the final improvements were finished, the prototype vehicles were sent to theAutocar Company for production. The new vehicle entered production under the nameM3 Gun Motor Carriage (orM3 GMC).[8][10]
As the existing supply of M2A3 gun shields was insufficient to meet requirements for the production of the M3, theOrdnance Department developed the M5 gun shield, which replaced the M2A3. The new design was designated as theM3A1 Gun Motor Carriage (M3A1 GMC).[9][11][12]
The T12/M3 GMC first saw action with the U.S. Army in the Philippines in 1941–42, six months after it was designed. Fifty were shipped on convoys to the Philippines in the late summer and fall of 1941. Three battalions of theProvisional Field Artillery Brigade operated T12s against the Japanese when they invaded the Philippines. During the early part of the campaign, the vehicle was used to provide direct covering fire and anti-tank support. The Japanese captured a few vehicles in 1942 and used them in thedefense of the Philippines.[9]
By 1942, M3 GMCs were being used bytank destroyer battalions in theNorth African Campaign, each of which consisted of 36 M3 GMCs and four37 mm M6 GMCs. The M3 GMCs, which were designed for ambushing tanks, proved to be inadequate for this task in the battles ofSidi Bou Zid andKasserine Pass, mainly due to poor tactics. Nevertheless, the M3--and the newly-introduced 3-inch M10-- were later used in theBattle of El Guettar with success, claiming 30 German tanks, including possibly twoTiger tanks, at the cost of 21 M3s and some M10s. Some M3s also saw service inAllied invasion of Sicily (Operation Husky), but by that time, theM10 tank destroyer had replaced it in the U.S. Army.[13] A total of 1,360 M3 GMCs were also converted back into M3A1 half-tracks.[14][15]
The M3 also served with theU.S. Marines in thePacific theater of Operations and was first used in theinvasion of Saipan. It proved highly effective against the JapaneseType 95 Ha-Go light tank and theType 97 Chi-Ha medium tank, in the fight against the Japanese 9th Tank Regiment on Saipan. It also served in theBattle of Peleliu and theBattle of Okinawa, and many other conflicts in the Pacific.[16]
The M3 GMC saw limited service with other countries as it was not widely supplied through theLend-Lease program. A small batch of 170 vehicles was supplied to Britain, which used them in theirArmoured Car Regiments which were the reconnaissance units of the armored formations. They were first used in theTunisian Campaign with theRoyal Dragoons. They were also used in Sicily,Italy, and later inFrance, but were gradually retired. TheFree French Army also used M3s for training before receiving M10 tank destroyers.[16] With two issued per squadron in practice they were used as an eight gun regimental artillery battery.[17]
A total of 2,202M3 GMCs were produced from 1941 to 1943. Only 86 vehicles were produced in 1941, but production increased to 1,350 in 1942, with the remaining 766 completed in 1943. Production was stopped due to the introduction of turreted, purpose-built, tank destroyers, such as theM10 GMC.[18]
| Month | Aug | Sept | Oct | Nov | Dec | Total |
|---|---|---|---|---|---|---|
| M5 | 61 | 25 | 86 |
| Month | Jan | Feb | March | April | May | June | July | Aug | Sept | Oct | Nov | Dec | Total |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| M5 | 1 | 150 | 229 | 274 | 178 | 49 | 112 | 139 | 119 | 90 | 9 | 1,350 |
| Month | Jan | Feb | March | Total |
|---|---|---|---|---|
| M3 | 291 | 150 | 75 | 766 |
