T30 Howitzer Motor Carriage

The T30 Howitzer Motor Carriage (HMC) was a United States Army Self Propelled Gun used in World War II. It was based on requirements for an assault gun issued by the Armor Branch in 1941. It was simply a 75 mm Pack Howitzer M1 in an armored box mounted on a M3 Half-track. The fuel tanks were moved to the back of the M3 Half-track. It debuted in the North African Campaign in November 1942. Some were leased to Free French forces and the type was used as late as the First Indochina War in 1951.

Specifications
The specifications of the T30 were similar to the specifications of the M3 Half-track. The dimensions were 6.28 m long, 1.96 m wide, and 2.51 m high, and the weight was 20,500 lb. The suspension consisted of vertical volute springs for the tracks and leaf springs for the wheels, with a fuel capacity of 60 USgal. It had a range of 150 mi and had a speed of 40 mph. Powered by a White 160AX, 147 hp, 386 in3, 6-cylinder, gasoline/petrol engine, with a compression ratio of 6.3:1 it had a power-to-weight ratio of 15.8 hp/tonne.

Gun specifications
The design overall of the T30 was the same as the M3 Half-track but the difference was the gun. The 75 mm M1 Pack howitzer that was mounted could depress 9 degrees, elevate 50 degrees, and traverse 22.5 degrees to each side. The vehicle had stowage for 60 rounds of 75 mm ammunition, and although it was not designed for anti-tank use, it had a high explosive anti-tank (HEAT) shell that could penetrate 3 in of armor at normal ranging. The gun shield had 0.375 inch armor, designed to stop a .30 cal bullet from 250 yds away.

Development
The T30 HMC was originally conceived in 1941 by the Armor Branch as an assault gun to equip tank and armored reconnaissance units. As a satisfactory design was close to a year away, the Ordnance Department decided to make an alternative design based on the M3 Half-track. The pilot vehicle came off the production lines in October 1941 armed with an M1A1 75 mm Pack Howitzer and its mounting design to fit a simple box mount on an M3 Half-track. It was authorized for production in January 1942, while the first deliveries to the Army came one month later. It was never type classified because it was viewed as a temporary solution. In September 1942 the T30 was partially replaced by the M8 HMC. After that it was declared as substitute standard. Around 500 were produced.

Service history
The T30 HMC entered service in November 1942. In one encounter, the T30 was used in an attempt to destroy German tanks. Although the T30s fired several volleys, the German tanks were barely damaged; as a result, the Army learned that low-velocity howitzers were ineffective against most tanks. In the 1st Armored Division, each regiment was issued 12 T30s. Of these, three were used in each headquarters platoon and three were used in each regimental reconnaissance platoon. The 6th and 41st Armored Infantry Regiments were also issued nine T30s apiece, with three in the HQ platoon of each battalion. Infantry divisions in North Africa deployed a cannon company with six T30s and two T19 105 mm HMCs. The T30 also served during the Allied invasion of Sicily in 1943 and the 1944 Allied invasion of Italy. It was removed from infantry division use in March 1943 because of the reconstruction of infantry battalions. The T30 was eventually replaced by the M8 HMC which was based on the M5 Stuart light tank. Deliveries of the M8 began in November 1942. Only 312 T30 HMCs were delivered in their original configuration, as the last 188 were converted back into M3 Half-tracks before they were delivered. Later on, the US leased several to Free French forces and some were used as late as the First Indochina War.