M4 Sherman

Introduction

The M4 Sherman was the primary tank produced by the United States for its own use and the use of its Allies during the early and middle parts of World War II although it was supplemented by the M27 Sheridan during the later stages of that conflict. Production of the M4 Medium tank exceeded 50,000 units, and its chassis served as the basis for numerous other armored vehicles such as tank destroyers, tank retrievers and self-propelled artillery. The M4 was dubbed the Sherman after Union General William Tecumseh Sherman, following the practice of naming tanks after famous American Civil War generals. The M4s simplicity and reliability meany that many nations continued to use the tank in both training and combat roles into the late 20th century. Ironically, it outlived its intended successor, the M27, by many decades.

Early Developments

The US Army Ordnance Department designed the Medium Tank M4 as a replacement for the Medium Tank M3. Detailed design characteristics for the M4 were submitted by the Ordnance Department on 31 August 1940, but development of a prototype had to be delayed so final production designs for the M3 could be finished, and the tank put into full scale production. On 18 April 1941 the final design characteristics for the new tank were approved at a conference at Aberdeen Proving Grounds attended by representatives of the Armored Force and the Ordnance Department. The stated goal was to produce a fast, dependable medium tank that was capable of defeating any other tank currently in use by the Axis nations. The first pilot model of the M4 was completed on September 2, 1941. The M4 was standardized and placed into production in February 1942.

Early Shermans mounted a 75 mm medium-velocity general-purpose gun. Later M4A1, M4A2, and M4A3 models received the larger T23 turret with a high-velocity 76 mm gun M1, which traded reduced HE and smoke performance for improved anti-tank performance. Later M4 and M4A3 were factory-produced with a 105 mm howitzer and a new distinctive mantlet in the original turret. The first standard-production 76 mm-gun Sherman was an M4A1 accepted in January 1944 and the first standard-production 105 mm-howitzer Sherman was an M4 accepted in February 1944.

The Sherman's armor was effective against most early war tank guns, the frontal thickness was the gun mantle at 91 mm, frontal turret 76 mm, and frontal hull 63 mm. The Sherman's frontal armor was designed to withstand a 50 mm gun, which was a common German anti-tank gun and the gun on the Panzer III medium tank during the North African Campaign in 1942. However, the Sherman's armor, while good for an early war tank, was inadequate against the German 75 mm KwK42L70, used only on the Panther tank, and the famous 88 mm used on the Tiger tanks. It was this deficiency in its frontal armor that made the Sherman very vulnerable to German high velocity 75 mm and 88 mm tank guns that the German Tigers and Panthers were equipped with in 1944. The Sherman's armor was not invulnerable to the 75 mm KwK40/42 used on the German Panzer IV-G/J series vehicles, but could take a hit and have time to react, unlike being instantly destroyed by a high velocity 75 mm or 88 mm shell. The lower velocity of the earlier Panzer IV guns and their thin armor's vulnerability to the Sherman's main armament gave Sherman a competitive edge against the most common German tanks.

Early Variants

M4/M4A1 Sherman;

33.4 ton medium tank armed with 75mm L38 Gun in fully enclosed rotating turret. Developed from T6 medium tank prototype. Tanks with a welded hull were designated M4; while those with cast hulls were designated M4A1. Well sloped front hull. 5 man crew consisting of Commander, Gunner, Loader, Driver, and Assistant Driver. Height was considered somewhat excessive; but this was due to having to accommodate the Continental R975 radial engine adapted from aircraft use. Required a decently trained driver to handle the engine in combat situations, due to the engine not being well suited for tank use. First combat-ready tank accepted in February 1942. Saw first action with the Russian Army in the summer of 1942. Was shown to be a very well designed tank, on par with Russian T-34. Production continued into late 1943/early 1944; depending on the plant. From late 1944 onwards; the survivors were converted into specialized vehicles as improved Shermans became available.

M4A2 Sherman

33.5 ton medium tank. Further development of M4 series. Due to Russian demands, and also to improve logistical commonality between US and Russian tank units; this was the first diesel powered Sherman; powered by a GM 6046 Diesel, which was in reality two GM 6-71 truck engines linked together. One oddity was that they could be run independently of each other if the user wished so. Due to feelings over the complexity of the twin engine layout and later tests showing that the 6046 was highly sensitive to dirt, resulting in poor reliability; the majority of M4A2 production was split between training units in the United States and Russian Lend-Lease deliveries; who wanted diesel powered tanks, even if they had flaws.

M4A3 Sherman

33.35 ton medium tank. Further development of M4 Series. Equipped with the Ford GAA V-8 gasoline engine. The GAA was much more easier for drivers to handle than the earlier Continental radial, especially on hills.

M4A4 Sherman

34.85 ton medium tank. Due to concerns over engine deliveries being unable to meet the projected production demands of the Sherman, a decision was made to produce a version of the Sherman using the Chrysler A57 Multibank engine. This was essentially five Chrysler engines bolted together. In the early production 'A4s, many minor maintenance procedures were impossible to perform unless the engine was removed from the vehicle to allow access to out of the way parts. Despite many of these problems being fixed in later productionized versions of the A57; the decision was made to relegate the A4 to training duties, with the majority of the A4s built turned over to the Philippine Army as part of the general strengthening of forces in the Philippines.

M4A5 Sherman

34.85 ton medium tank. Further development of M4 Series. Powered by the Caterpillar DAA V-8 Diesel, which was a modified Ford GAA engine which could run on a variety of fuels; from crude oil to 100 octane aviation gasoline. Penultimate development of the Early Series Shermans; and the most mass produced of them all.

M4A5(105) Sherman.

Standard M4A5 equipped with 105mm howitzer in place of the 75mm gun.

Improved Shermans

In early 1942; Aberdeen Proving Ground submitted it's proposal for an improved M4 type medium tank. Weight would increase to 41.8 tons, and it would be powered by a 640 hp G200 radial engine. Armament would remain the same as the earlier M4; a 75mm L38 gun. Armor protection was increased around the final drive housing; and the hull sides were angled to give protection equivalent to 2.5 inches of armor. This proposal was rejected within moments of it being given to the Armor board. The reasons given for rejection were:

  • No increase in frontal protection.
  • No increase in firepower
  • 6.15 ton increase in weight, which also tied into 1 and 2.

Detroit Arsenal also submitted it's own design, which while keeping to a more manageable 30.5 ton weight; offered little else but detail improvement such as rearranging the armor for slightly better protection on the frontal slope by eliminating the bulges over both driver's positions; and angling inwards the sponsons; requiring an increase in vehicle width to 120 inches. This too was rejected as requiring too many changes in the production line for too little increase in capability.

However, at this point, the design of the M-4 series was influenced by the parallel development of the T20 medium tank program that eventually culminated in the T26/M26 Pershing. This was initially something of a leisurely development but the demands of the Russian Front forced the program onto an entirely different track. The pressure of events forced Ordnance and Armor to produce the M-26 Pershing that had the armor and firepower of the Tiger I, but weighed in at 16.7 tons less.

In July 1943, it had been proposed to standardize the T23E3 as the medium tank M27 with the electric drive and torsion bar suspension. At the same time it was proposed to standardize the T20E3 as the medium tank M27B1 with the torqmatic drive and torsion bar suspension. An OCM item was drafted, but standardization of the electrid drive M27was not approved. The M27B1 was produced as the standard M27, this produced a tank that had an improved 76mm gun but was 1.75 feet lower in overall height, and at a combat weight of 33.8 tons; and having the following specs:

100mm Hull Frontal Equivalent
50mm Hull Sides
89mm Turret Frontal Equivalent

At this point light dawned on the designers. Since the M4/T20E3/T23E3/T26 all shared the same diameter turret ring it would be possible to produce M-4 Shermans that were armed with either the 76mm gun from the T23E3 or the 90mm gun from the T26.

Later Variants

M4A6 Sherman HVSS

New-build M4A5 Sherman hulls equipped with the T23E3 76mm turret. These saw service in Russia from mid-1944 onwards.

M4A7 Sherman HVSS

Existing M4A5 Sherman Hulls reequipped in ordnance depots in Russia with 90mm T20E3 turrets shipped over from CONUS. Combat weight of about 38-39 tons; just about too heavy for existing shipping and cranes. Top heavy, and disliked by their crews due to absurdly high center of gravity.

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