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M40 Gun Motor Carriage

1945 COLD WAR KOREAN WAR SELF-PROPELLED ARTILLERY WORLD WAR 2

History of the M40 Bolt Frame

With the conversion of the M3 Lee medium tank into a successful 155mm armed M12 artillery motor vehicle, work began on an improved tank based on the better M4 Sherman chassis. However, the M3 conversion uses existing stocks of older French M1917 guns that are well past their prime and predictably in short supply. Thus, the 155mm M1 "Long Tom" rifle was paired with the Sherman M4A3 model chassis to create the "M40 Gun Motor Carriage" - known as the "155mm Gun Motor Carriage M40" in the official U.S. Army name.

While retaining many of the Sherman M4A3's components, the fuselage was slightly wider to make up for the massive gun and mounting hardware.

The M40 came in the form of the "T83" prototype. Upon successful completion, the vehicle is put into service as an M40. However, it was not shipped to Europe in sufficient quantities for combat use - in fact, only one prototype was used for combat use. The Pressed Steel Car Company produced some 311 prototypes (some say as many as 420)the first was in February 1945but these arrived too late to be used in the conflict, and U.S. military materiel The sharp drop in the entire vehicle production led to a planned 600-person inventory. The M40 was not standardized in U.S.

Army service until May 1945.

Nonetheless, the M40 replaced the outgoing M12 models, which also entered service with the British Army (as "155mm SP, M40 Cardinal"). By the time of the Korean War (1950-1953) it was available in abundance and it served ground forces well.

When completed, the M4 Sherman origin of the M40 can be clearly identified, especially on the front sloping glacis panel. The landing gear consisted of six wheels on one side of the fuselage, with the drive sprockets at the front and track idlers at the rear.

The crew consisted of eight people, including the driver, commander and up to six gunners. All in all, the car weighed about 40 tons and was equipped with 12mm armor protection and a 155mm main gun barrel. Measurements include a length of 29 feet 10 inches, a width of 10 feet 4 inches, and a height of 8 feet 10 inches. Power is provided by a 340-horsepower Continental R975 EC2 gasoline engine.

This gives the vehicle a maximum road speed of 24 mph and a range of 105 miles. Suspension is the same horizontal coil spring suspension (HVSS) as the Sherman M4A3 model.

The 155mm gun fired 95lb HE rounds at 25,175 yards. It sits on a complex recoil mechanism and a structure that allows it to reach the desired height. The storage space on board can transport 20 large 155mm shells, so the M4A1 tractor is used to tow the M23 ammunition trailer.

The T89 Howitzer Motor Vehicle Mount (detailed elsewhere on this page) is a related M40 development, albeit with a more powerful 203mm howitzer system. The vehicle was standardized in November 1945 - as it could not be used in World War II - and was designated as the M43 Howitzer Motor Transporter.

These chassis can be converted back to M40 form if desired.