75 mm Howitzer Motor Carriage T30 - Tank Encyclopedia (2025)

United States of America (1942 – 1945)
Howitzer Motor Carriage – 500 Built

At the start of the Second World War, the US military identified a need for mobile and adaptable forces in response to the German Blitzkrieg. As a result, a rapid rearmament and modernization effort was launched, which, among other things, led to a project to mount a 75 mm field howitzer on the M3 Half-Track, resulting in the development of the 75 mm Howitzer Motor Carriage T30. The T30 HMC saw action in North Africa and continued to serve throughout the Sicilian and Italian campaigns, and supported Allied operations until the end of the war.

Context

75 mm Pack Howitzer M1A1

After World War One, the US Army began developing a replacement for their British Vickers-Maxim 2.95 in. gun (74.9 mm), which served as a pack howitzer. Pack howitzers were intended to be used in difficult terrain, such as mountains, where normal guns were not practical. Another feature of pack howitzers was that they were able to be dismantled to be carried by mules or horses (this led to other armies calling them mountain guns). In 1920, this effort led to the development of a new 75 mm pack howitzer, completed and standardized as the 75 mm Pack Howitzer M1 in August 1927. However, it was severely limited, so M1s were not produced on a large scale, with only 32 being made by 1933, and by 1940, only 91 M1s were available. The M1 was upgraded to the M1A1, mainly with upgraded breach blocks and rings. This entered production in September 1940 and became the main pack howitzer in US service.

Half-Tracks

The First World War demonstrated a need for a vehicle to take infantry into combat. The main options were trucks, which could not cross rough terrain, or tracked vehicles, which were too expensive. This resulted in experimentation with half-tracked vehicles, which offered a balance between cost and cross-country mobility. In 1925 and 1931, the Ordnance Department examined Citroën’s Kegresse half-tracks. As a result, the Ordnance Department authorized various companies to create test vehicles and then issued some to the Field Artillery, Signal Corps, and Cavalry. The Ford Motor Company built the Half-Track Truck T9 in 1936. This was standardized as the Half-Track Truck M2. The Half-Track Truck M2 used front wheel drive with a powered axle, allowing the track to be synchronized with the front wheels. Rock Island Arsenal and the White Motor Company then created the Half-Track Personnel Carrier T7 in 1938, using an M2A1 Scout Car with the rear suspension units swapped out for tracks and adapted the power train from the Half-Track Truck M2. This was tested and further modified but was later returned to a scout car. The Ordnance Department authorized the Half-Track Scout Car T14 in December 1939, which was created in early 1940 and tested in September 1940. This led to the T14 to be standardized as the Half-Track Car M2, which was upgraded to the Half-Track Car M3 by extending the body and frame by 25.4 cm (10 in.), production of which began in May 1941.

The M3 Half-Track would become one of the most important vehicles for the US because of the sheer amount of vehicles produced, with 15,253 produced as the M3 series alone. The main purpose of the M3 Half-Track was to transport troops into battle and then leave. However, it would be used to carry various types of guns, including artillery pieces, anti-aircraft guns, and anti-tank guns, or ammunition for self-propelled guns, with only these being its official duties. Unofficially, troops in the field would use the M3 Half-Tracks for a large amount of other purposes, including as an ambulance, command vehicle, and propaganda, among other roles.

Half-Track Cun Motor Carriges

The escalating conflict at the start of the Second World War showed the need for mobile, responsive forces, contrasting the more stationary traditional artillery. In 1940, in response to the German Blitzkrieg, the US military rapidly began a rearmament and modernization campaign. This led to the foundation of the Armored Force in 1940 and reintroduced self-propelled field artillery. Initially, this led to the 75 mm Gun Motor Carriage T12, later standardized as the 75 mm Gun Motor Carriage M3, an M3 Half-Track with a 75 mm gun, which was considered successful.

Development

In October 1941, the Armored Force Board made a request, which was subsequently approved by the Chief of Staff, for a program to mount a 75 mm field howitzer into an M3 Half-Track in a manner similar to the T12 GMC.

The Ordnance Committee set the military characteristics on 6 January 1942 in OCM 17665 and designated it the 75 mm Howitzer Motor Carriage T30 in OCM 17665. Two pilot models were then authorized in OCM 17809. The armament was the 75 mm Howitzer M1A1, using an M1A2 recoil mechanism, mounted on a 75 mm Field Howitzer Carriage M3A1. This would allow the gun to traverse 21° left and 23° right and elevate -7° to 50°. Autocar built these pilots. One was sent to Aberdeen Proving Ground (Maryland) to design and test a shield, and the other was used as a manufacturing pilot by the White Motor Company.

On 23 March 1942, likely due to viewing a pilot, it was requested that the shield be shortened by at least 15.2 cm (6 in.). This was completed, but to accomplish this, the elbow telescope was removed. However, this led to a request to investigate mounting an M5 elbow telescope. This returned the T30 HMC’s shield to its original height. The shield was then extended 23.2 cm (8 in.) rearward. The side armor lowered to within 6.35 mm (0.25 in.) of the vehicle sides, which was later increased to 19.1 mm (0.75 in.). An armored flap was also added above the tube.

Aberdeen Proving Ground conducted extended firing tests, which showed only a few small suggested changes. It recommended that the T30 HMC be produced as an expedient howitzer motor carriage until a better vehicle was available.

Production

The US Army decided that 42 T30 HMCs would be issued to each armored division, with 60 remaining in reserve. As a result, a contract was issued to the White Motor Company by amending contract W-303-ORD-945 (originally issued for M3 Half-Tracks) with production order T-3212. This initial contract was for 312 T30 HMCs with serial numbers ‘4004’ through to ‘4303’ (and twelve without serial numbers) and registration numbers ‘409582’ to ‘409893’. The first batch of 312 were completed from February to April 1942. However, 108 more were ordered to be converted from M3A1 Half-Tracks under Production Order T-19179, which was completed by August 1942.

Another batch was made by amending contract W-303-ORD-1611 with Production Order T-3967 to make 188 T30 HMCs. However, these were transformed back into M3A1s, which were delivered in November 1942, although only 80 are known. These had serial numbers ‘315’ to ‘394’ and registration numbers ‘4042505’ to ‘4042584’. Oddly, a single T30 HMC was later converted to an M3A1 Half-Track under W-11-0220-OED-3630, Production Order T-19179.

Design

The T30 used a roller on the bumper to help prevent the vehicle from being stuck. Behind this was the engine compartment with front-mounted louvers. The sides could open to allow maintenance. Mounted to either side of the engine were the wheels and fenders. These fenders held the headlights, which were the stronger tank models to withstand the gun blast. To allow the gun to depress, the armored windshield was hinged from the bottom. The armored windshield otherwise protected the driver’s compartment, which had two seats and driving controls, along with two doors. The driver’s compartment doors were of a two-part design with the lower part hinged to the vehicle, and the other part was folded down to allow greater vision. Behind the driver’s seat was the howitzer mount, located between the benches on either side of the vehicle. From the middle to the rear, between the benches on either side, was a raised platform with space for rounds underneath, with a machine gun post. On either side of the rear was a fuel tank, and on the center of the rear wall was a door, which was close to the machine gun post.

The T30 HMC was 6.1 m (240.1 in.) long, 2 m (77.25 in.) wide, and 2.29 m (90 in.) tall. It had a combat weight of 9.3 tonnes (20,500 lbs.). The armor used rolled face-hardened steel assembled using bolts.

Engine and Suspension

The T30 HMC used a White 160AX engine, which produced 147 hp at 3,000 rpm using six in-line cylinders with 72 octane gasoline. This power was transferred through a Spicer 3461 constant mesh transmission, which featured four forward speeds and one reverse. The engine was fed from two fuel tanks in the rear, which held 227.1 l (60 gals).

The T30 HMC was controlled with hydraulic brakes and a steering wheel. On the front, the suspension comprised a semi-elliptic longitudinal leaf spring and shock absorbers. The rear suspension used bogies, which used vertical volute springs. These rode on eight road wheels in pairs on two arms and a Kegresse-type track, composed mainly of one piece of rubber, which was 304.8 mm (12 in.) wide.

The T30 had a range of approximately 322 km (200 miles) and could reach a maximum speed of 72.4 km/h (45 mph). It was capable of overcoming an obstacle 304.8 mm (12 in.) high, with a maximum grade of 60%, traveling through water 81.3 cm (32 in.) deep, and had a turning diameter of 18 m (59 in.).

Armament

The T30 HMC was armed with the 75 mm Howitzer M1A1 on a T10 Mount, which was aimed directly by an Elbow Telescope M5 and indirectly by the Panoramic Telescope M1, Range Quadrant M3, and Gunner’s Quadrant M1. The T30 HMC carried 60 75 mm rounds and could fire eight rounds a minute. More rounds could be held in a trailer or accompanying half-track, which could pull an additional trailer. The mount allowed the gun to elevate manually -9° to 45.9° and it had a traverse of 22.5° to either side. Likely as an anti-aircraft gun, a 12.7 mm (0.5 in.) M2 machine gun (with 300 12.7 mm (0.5 in.) rounds) could be placed on a pedestal mount M25 in the rear of the vehicle.

The rounds the M1A1 could fire were: HEAT (high-explosive anti-tank) M66, Smoke (sulfur trioxide or white phosphorus) or Gas (hydrogen) M64, WP (white phosphorus) or Persistent Gas M57, HE (high-explosive) M48, HE M41A1, Drill Cartridge M19, Ammunition Blank M2A2.

Crew

The T30 HMC had a crew of five: driver, chief of section, gunner, and two cannoneers (the artillery term for loader). If there was an accompanying ammunition carrier, it would have a driver, ammunition agent, and two more cannoneers. The crew communicated with the SCR510 radio and flag set M238. The T30 HMC had provisions for the following small arms for the crew: 11.43 mm (0.45 in.) M1928A1 submachine gun with 500 11.43 mm (0.45 in.) rounds and four 7.62 mm M1 rifles or M1 carbines.

Service

The US employed three half-tracks with artillery pieces mounted. The T19 HMC and T30 HMC acted as heavy and light artillery (respectively) and the 75 mm Gun Motor Carriage M3 acted as a tank destroyer. The T19 HMC used a larger 105 mm howitzer and rounds than the T30 HMC, meaning it had more explosives in the round, but it would be heavier and take longer to load. Contrasting this, the T30 HMC used a nearly identical layout but with the ability to carry more rounds (8 compared to 60 without trailers) and fire faster due to its smaller size. While the M3 GMC shared a similar layout to the T19 and T30 HMCs, they primarily engaged tanks from long range, although tank destroyer crews were trained for indirect fire.

The T30 HMC served in North Africa alongside the M3 GMC and the T19 HMC. It was part of the First Armored Division, which was assigned a dozen, of which three were assigned to the regimental reconnaissance battalions and tank battalion headquarters platoon. In addition, the 6th and 41st armored infantry regiments had nine assigned to each, three of which were assigned to the regimental reconnaissance battalions. The T30 HMCs that were not deployed likely stayed in the United States, possibly being used for training.

The T30 HMC first entered combat during the November 1942 Operation Torch invasion of North Africa, where they supported infantry during the landings at Oran and Algiers. Later, the T30 HMC participated in battles near Kasserine Pass in February 1943 and in fighting near El Guettar in March 1943.

The introduction of the 75 mm Howitzer Motor Carriage M8 (M8 HMC) began to replace the T30 HMC in March 1943, with some units using towed guns between the switch from the T30 HMC to the M8 HMC. However, the T30 HMC followed the Allies into the invasion of Sicily in 1943 and the Italian campaign in 1944, which saw at least one T30 HMC with the 157th Infantry Regiment, seemingly making it into Germany by 1945.

Like with the T30 HMC HMC, the M8 HMC made use of an existing chassis, the Light Tank M5 Stuart, it differed in the fact it was significantly different from the base vehicle with a new turret and partly redesigned interior. The M8 HMC used the later M3 Howitzer, which could fire the same ammunition M1A1 Howitzer with similar performance, however, it could traverse 360° and elevate from -20° to 40° which was mostly superior to the T30 HMC (traversing 45°, 22.5° to either side, and elevating -9° to 45.9°). Another benefit was the fact that the M8 HMC was based on the M5 Stuart Light Tank this likely simplified maintenance because it shared a chassis tank units were already familiar with. The M8 HMC used two Cadillac V8 car engines which mechanics may have been familiar with.

Other Users

A small number of T30 HMCs were supplied to the Free French, which likely served into the early 1950s, when they were deployed to Indo-China (now Vietnam).

At least one T30 HMC was captured in Tunisia by German forces.

Conclusion

The 75 mm Howitzer Motor Carriage T30 played a crucial role in the US military’s transition to more mobile and versatile forces during the Second World War. Initially developed as a stopgap measure, it proved effective in early operations in North Africa and continued to serve through the Sicilian and Italian campaigns. Though eventually replaced by more advanced models, such as the M8 HMC, the T30 HMC helped demonstrate the value of self-propelled artillery.

Sources

Documents

TM 9-1901 ARTILLERY AMMUNITION, WAR DEPARTMENT, 29 June 1944

Books

RP Hunnicutt, 09. Half-Track – A History of American Semi-Tracked Vehicles, Presidio Press, Novato, 2001, pages 118-121, 219, and 233
David Doyel, U.S Half Tracks Part Two, The Ampersand Group Inc, 2016, pages 87, 89, 247, and 249
Steven J. Zaloga, 201 – M7 Priest Howitzer Motor Carriage, Osprey Publishing, Oxford, 2013, page 4-6
Steven J Zolaga, 011 – M3 Infantry Half-Track 1940-73, Osprey Publishing, Oxford, 1997, page 37
Steven J Zolaga, US Field Artillery of World War II, Osprey Publishing, Oxford, 2007, page 6 and 7
Michael Franx, U.S. WWII HALF TRACK Cars M2, M2A1, M9A1 & Personnel Carriers M3, M3A1, M5, M5A1, Tankograd, Erlangen, 2007, page 2
Michael Franz, 75 mm Howitzer Motor Carriage M8 HMC, Tankograd, Erlangen, 2008