Medium Tank M3A1

The Medium Tank M3A1 was the only version of the Medium Tank M3/ Grant/ Lee to use a cast upper hull.

The original M3 was constructed from sheets of rolled armour that was riveted together, but the turret was built using cast armour. This led to work on the idea of using larger castings for at least part of the hull. A test hull was produced using cast open hearth steel, and subjected to ballistic tests. These showed that the cast armour had to be slightly thicker than the rolled armour to provide the same level of protection, but the curved shaped allowed by the casting saved an equal amount of weight. The use of cast armour for the upper hull also reduced the danger of fragments of rivets bouncing around the inside of the tank during battle.

In June 1941 the Ordnance Committee approved the use of cast upper hulls on medium tanks, and on 9 October 1941 the M3 with cast hull was designated the M3A1. As first built the M3A1 was similar to the original M3, although the different shape of the hull meant that a hatch on the hull roof had to be moved from the right hand side to the right-rear. The original M3A1 had side doors in the hull and un-armoured rotors for the two main guns.

During its production run the side doors were eliminated from the hull. Early experience with the M3 had shown that dangerous levels of gasses built up inside the hull when both main guns were being fired, and three extra ventilators were added. Late production M3A1s also had these ventilators added, although the altered position of the roof hatch meant that one had to be moved forward.

The M3A1 entered production at the American Locomotive Company in February 1942, and 300 were built before production ended in August 1942. The British gave the M3A1 the designation General Lee Mk II, although none appear to have been delivered.

Between 2 July and 8 October 1941 one M3A1 was used for tests with the Guiberson T-1400-2, followed by a second tank between 30 April and 23 June 1942. The original aim had been to use this engine as an alternative power plant in the M3, M3A1 and M3A2, and the tests did show that it increased range and performance, but the engine was also found to be too unreliable. Use of the Guiberson engine was discouraged, and only 28 of the M3A1 (diesel) variant were produced. The diesel powered M3A3 used a different power plant, made up of two General Motors diesel engines mounted side by side.

Stats
Production: 300
Hull Length: 222in with Gun M2, 241in with Gun M3
Hull Width: 107in
Height: 123in
Crew: 6 or 7
Weight: 63,000lb combat loaded
Engine: Wright Continental R975 EC21, 9 cylinder air cooled
Hp: 340hp at 2,400rpm
Max Speed: 21mph sustained, 24mph max
Max Range: 120 mile cruising range, roads
Armament: 75mm Gun M2 or M3 in front right of hull, 37mm Gun M5 or M6 in turret; three .30in machine guns - one in turret cupola, one coaxial in turret, one in hull front

Armour

Armour

Front

Side

Rear

Top/ Bottom

Turret

2.0

2.0in

2.0in

0.875in

Superstructure

 

 

 

 

Hull

2.0in

1.5in

1.5in

1.0in

Gun mantlet

 

 

 

 

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How to cite this article: Rickard, J (16 June 2016), Medium Tank M3A1 , http://www.historyofwar.org/articles/weapons_medium_tank_M3A1.html

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