M40/M43

M40 GMC with the 155 mm Gun M1.

The production of the M12 self-propelled gun exhausted the Army's supply of M1917/M1918 155 mm guns. But the chassis proved to be unsuitable for the newer, more powerful 155 mm Gun M1, so a replacement was sought. It was suggested to use the T23 medium tank as a self-propelled mount for the M1 gun, but this was rejected. Further study showed a new chassis could be developed using M4 Sherman components.

On 18 March 1944, five pilot vehicles were authorized as the 155 mm T83 Gun Motor Carriage. The hull was open except for the driving compartment, which was located forward of the engine. The armor was reduced compared to that of the M4 Sherman, being only 1/2 inches thick at the front. Tests with the first pilot showed the T83 to be extremely satisfactory. After 200 rounds of test firing, the 155 mm gun was replaced with the 8-Inch Howitzer M1. This howitzer also proved to be successful and the T83 armed with this weapon were redesignated as the T89 Howitzer Motor Carriage.

The T89 was designated as a universal chassis, which could mount either 155 mm or 8-Inch weapons. All components were designed to suit the needs of either weapon, including ammunition stowage and the travel lock. In February 1945 the T83 was authorized for production. 418 vehicles would be delivered before the end of the year, with 24 being converted into T89s. The T83 was standardized as the M40 in May 1945, with the T89 standardized as the M43 later in November.

M43 armed with the 8-Inch Howitzer M1.

Although production of the M40 and M43 were too late for use in WWII, two pilot vehicles did see action in Cologne. From there, they saw service in the Korean War.

Combat trials in Cologne showed the M40 was vulnerable to artillery bursts and small-arms fire, an issue that was also prevalent for the M12. To provide overhead protection, an experimental armored cab was installed on the second pilot. There were several different thicknesses considered for the cab: 1/2, 3/4, and 7/8 inches, which weighed 3151, 5134, and 7712 pounds respectively. The latter of which would ultimately be selected. However, various parts of the recoil mechanism and equilibrator were still exposed and vulnerable. Because of this, the armored cab was rejected.

This tank, the M40/M43, is very much the same as the old version at Tier VIII. However, in order to fit better at Tier IX, it would receive some improvements to its gun handling and characteristics, and traverse speed. However, the tank also gets the new armored enclosure as an alternate hull option. This would improve the hitpoints of the vehicle, yet clearly make the tank an easier target.

The M40/M43 also continues the split-trend established by the T79/T80.

Guns: 155 mm Gun M1; 8-Inch Howitzer M1

Engines: Continental R-975-C1 (350 hp); Continental R-975-C4 (460 hp)

Suspensions/Alternate Hulls, Total Weight (metric tons): M40 HVSS (36.3); M40 HVSS Shielded (39.8)

Hull Armor (mm): 108/13/13

Top Speed: 39 km/h

Crew: 6 (Driver; Gunner; Loader; Loader; Commander; Radio)



Parent: T79/T80
Children: T92/T93
See Also: T84 HMC

Sources:

Hunnicutt, R. P., Sherman, 1995