Early production M2 medium tank. Notice the two extra turret mountings. The total was a staggering 9 Browning M1919 cal.30 machine guns. However, they were only four gunners manning the entire arsenal, including two for the main M3 37mm gun. The M3 light tank was also heavily armed with machine guns by 1940 (5). But these features quickly lost favour.
M2A1, the main production serie, made at Rock Island Arsenal. This is the "Glamorous Gladis", from one training unit in early 1941, now preserved at the Aberdeen Proving Grounds. The main differences with the preserie M2 was the M2 light tank turret, some improvements in gun mantlet and glacis armor, and an upgraded Wright radial R-975 C1, supercharged. The M2A1 formed thousands of tankists during the early stages of world war II.
The M3/M5 history on Wikipedia
M2 MEDIUM TANK
Medium Tank - USA. 112 built 1939-40.
The M2 preserie :The future M2 design was fixed on the paper with the T5 prototype, designed at the famous Rock Island Arsenal, the federal government main weapons manufacturer and U.S. army foundry. Work started in 1938 as a new model based on the M2 light tank design. By june 1939, the prototype of the M2 Medium Tank was ready for trials, with a sloped hull wrapping a tall fighting compartment and a new 350 hp R-975 aviation radial engine. This m2 was limited to 18 deliveries, for evaluation by an US Army commission. The M2 borrowed many parts with the light M2, starting with the vertical volute springs suspension, which three of them were fitted to support the longer hull. The tracks were rubberized, as tests desmonstrated that rubber-shoed tracks has a quite better durability than metal ones. The aviation engine was far more powerful than the M2 light tank, notably to cope with the extra weight of a longer hull. It was chosen for the same reasons, as been compact, efficient, sharing parts with a largely produced and reliable model, also facilitating the maintenance procedures. The drawback never experience however by the M2 in the field, with its high octane aviation gasoline consumption, a highly volatile, yet flamable fuel.
M2 hull design :The M2 hull was a compromise between the vintage Liberty tank (Mark VII), co-developed by Britain, and the need of an anti-tank, fully traversing turret modelled on the M2 light tank. The tall hull was litteraly bristling with firepower, with no less than seven M1919 Browning standard cal.30 machine guns, and nine in maximal configuration. Two were fixed in the frontal sloped glacis, and another coaxial in the turret, with four more on a sponson-like superstructure, in ballmounts on each corner of the central fighting compartment. Two mounts were added early on (later seemingly remove in the M2A1) to both sides of the sloped turret, for anti-aircraft defence, bringing the total to a level never attained by any ww2 tanks before and after. To feed this impressive arsenal, no less than 12 250 cartridge were stored inside the lower storages boxes of the central casemate. But the main armament was the M3 37mm anti-tank high velocity gun, also borrowed, as the turret, to the light M2. It was fed with AP and HE rounds, which was armor-piercing at 500 yards (457m) over a 47mm sloped armor.
The armor was riveted, outside and inside (which presented a projection risk in case of a blast) with sloped surfaces around the central casemate. The frontal glacis was the true innovation of the time, artificially increasing the armor thickness by an inch or more. The driver sat directly on top of the tank's transmission, and was granted an excellent peripherical vision through three large armored folding panels. The glacis machine-gun muzzle was only protruding from a few centimeters, the entire lenght of the barrel was kept inside the hull. Both were actioned by the driver. Another odd feature, bullet deflector plates were installed on the rear fenders, a trench-warfare specificity wich proved soon useless. Other bullet deflectors were installed on the front mud guards and the sloped glacis. The armor was just 6.4mm on the bottom, internal compartment firewall, turret roof, and 20 mm on the sides, 30 mm on the frontal glacis, turret sides and gun mantlet. With its slope, the frontal armor was equivalent to 50mm in direct fire. The engine was fed by two internal tanks, for a total of 473 liters (126 US gallons).
Production of the upgraded M2A1 :In august 1940, the US Government contracted the newly-built Detroit Arsenal Tank Plant, owned by Chrysler, for a provision of 1000 units. However, with the war in Europe showing that the M2 design was already obsolete, the order was shifted to the M3 Lee, and production was resumed at the Rock Island Arsenal, where 94 M2A1 beeing ultimately produced. This was the modified version choosed by the army, with a revisited, thicker armor (the gun mantlet was now 51mm strong) larger turret, borrowed to the M3 light tank (M3 Stuart). The engine was also upgraded, the Wright radial R-975 C1 beeing supercharged to produced another extra 50hp, for a total of 400 (300Kw). The new larger turret also allowed extra pintle mounts to be fitted. However, lacking armor, having a high profile, and armed with a relatively small main gun and a collection of machine-guns in an obsolete configuration, the M2 compared poorely to other European tanks. But some features, like the chassis, engine, transmission and suspension, and more importantly, the frontal glacis design, had some strong influences on later design, starting with the M3 Lee, and the m4 Sherman.
Active service :Because of its limitations, the M2 medium tank never left the American soil, beeing registered by the ordnance as training machines. They served with the 67th Infantry Regiment training unit, and later with the 69th Armored regiment of the First armored division by 1941. Most officers and crews fighting in North Africa by 1943 with light M3s Stuart and medium M3s had been trained on these machines. By 1945, these machines were nearly all scrapped, but a handful survived, now displayed by the Aberdeen proving Grounds, Patton Museum of Cavalry and Armor, and the US Army Ordnance Museum.