On January 2nd, 1945 the US Army Ground Forces Equipment ReviewBoard outline requirements for a new class of tanks, and on June 20th they reportedthat they suggest that American Armored Forces have a 25 ton light tank, a 45ton medium tank, a 75 ton heavy assault tank, and wanted to research a 150 tonsuper heavy tank. In 1946, the Stilwell Board dropped the plans for the 150 tonvehicle along with tank destroyers and had American tank development looselyfollow the requirements set forth by the AGF up until requirements changed inthe year 1950.
So first off lets discuss the 25tvehicle. The AGF’s 25t tank was to replace the M24 which was inadequate,especially in the firepower department. The proposed gun was to be a 76 mmcannon that was to penetrate 127 mm @ 914 meters against a 30 deg. slopedplate. Mobility was also suppose to be better than the Chaffees. Iactually mentioned this project before in this article, because the AGF’s 25t proposal quickly developed intothe T37 and later into the M41 Walker Bulldog.
The 45t vehicle had some interesting features. First of all thearmor protection was very thick. The frontal hull was to have 203 mm thickarmor. There is some ambiguity whether this is to factor in slope or not. Thegun for this 45t tank is also very interesting. It was to be a high velocity 76mm cannon which could penetrate 203 mm @ 914 m against a 30 deg. sloped plate.I have concluded that this penetration requirement refers to HVAP shells ratherthan AP, but I could be wrong. The gun was also to be stabalized and was tohave a rangefinder. Another interesting piece of info is that this gun was tohave an autoloader, but was to retain all 5 crewmen. The 45t vehicle was tohave a remote controlled bow .30 cal MG as well as .30 cal “blisters” on theside of the turret.
Concept Art of the AGF’s 45t tank.
The 75 ton vehicle was another oddity. This behemoth was to have5 crew members and was to have a top speed greater than 30 km/h. The main gunwas requested to be a 90 mm gun that could penetrate 267 mm @ 1828 meters againsta 30 deg. sloped plate with HVAP shells. This is ~100 more mm than theT15E1/T15E2 guns in the same conditions with HVAP shells. Accuracy of the 75ttank was to be excellent. Reasonable accuracy was to be maintained up to rangesnear 3.5 km. The armor of the vehicles was to be equal to at least 267 mm atzero slope.
Proposed Armor Values.
I have touched on the 150 ton project before, but I forget whicharticle I mentioned it in. Anyways the 150t vehicle was to be armed withanywhere from a 105 mm gun to a 155 mm gun. Whatever gun was mounted, there wasto be a duel autoloading system(as in the T22 medium tank) for quick changesbetween ammo types. A stabilizing system was also to be used. Armor was to beas heavy as weight and mobility requirements allowed. The conceptual artfeatured in the June 20th report had a semi-trailer layout which was thought tobe necessary for transportation for a 150 ton vehicle.
In the title I called these tanks the American “E Series”. Onecan make parallels between the AGF’s proposals and Wa Pruef 6′s proposals fortanks based on weight class. Both projects had some actual vehicles built likethe T37 and parts of the E 10, E 25, and E 100; but a large amount of theseprojects’ attributes remain shrouded and ambiguous. I would also like to saythat the AGF likely never took the E Series into consideration when coming upwith these requirements. It is just a case of two groups coming up withsomewhat similar solutions to somewhat similar problems.