Medium Tank, M4 “Tompkins”
|Weight: Roughly between 32 to 33.5 tons||Height: 8 ft (2.4 m)|
|Width: 10 ft 1.5 in (3.1 m)||Length: 21 ft 6 in (6.6 m)|
|Crew: 4 (Commander, Gunner, Loader, Driver)||Entered Service: Sep. 17, 1941|
· Front: 2.5 in (63.5mm) at 56° from Vertical
· Side: 1.5 in (38.1 mm) to 1.7 (43.2 mm), Vertical
· Rear: 1 in (25.4 mm) at 20° from Vertical
· Front: 3 in (76.2 mm) at 56° from Vertical
o Front Armor Face angles out and to rear 3° from turret edge.
· Gun Mantlet: 2.3 in (58.42 mm) at thickest point, rounded.
· Sides: 2 in (50.8 mm) at 10° from Vertical
· Rear: 1.7 in (43.2 mm)
|Main Armament: 75mm L/47 M7
· Ammo Capacity: 64 rounds
· Barrel Length: 47 Calibres (3.5 m)
· Ammunition Used: AP, APC, HE
· M1919A5 .30cal on Left-side Coaxial Mount
· M2HB .50cal on standard pintle mount on Commander’s cupola
· Early Prototypes: Chrysler V12 Diesel
· Locally Produced Meteor Engine
|Fuel Capacity: 157 US Gal (594.3 L)||Speed: 31 mph (49.9 km/h)|
“The Tompkins is ugly as sin, something like the twisted minds behind Metropolis, art deco in armor. Until it gets shot at, and now you understand why everything is angled up and out.”
-Unknown Tank Commander, U.S. Dragoons (1943)
The Medium Tank, M4 “Tompkins” is an evolved ‘cruiser’ type tank in use by the United States Army Dragoon forces. Named after Civil War artillerist Captain John A. Tompkins, the M4 Tompkins fulfils the stated breakthrough and anti-armor role of the U.S. Dragoon’s Armor and Cavalry component. Designed primarily to escort the U.S. Dragoon forces as well as provide anti-armor support for the Dragoons and allied forces, the M4 Tompkins would eventually replace the Medium Tank, M2 “McGilvery” in Dragoon/Cavalry service and supplement the Heavy Tank, M6 “Sherman” in Infantry service by mid-1942.
The contributing factors to the M4’s success is its high mobility and speed, effective armor, powerful anti-tank gun, and the ease of which a unit can be built and its crew trained. Lessons learned from the M2 McGilvery were incorporated into the M4 Tompkins, and while initially fitted with a purpose-built Chrysler V12 diesel engine, technology exchanges with the United Kingdom eventually led to the usage of the ground-use version of the superb Merlin engine.
With the war going into full swing and the costly production of the Heavy Tank, M6 “Sherman” limiting the numbers produced (in comparison to other armored vehicles), the versatility of the Medium Tank, M4 Tompkins was fully realized when the overall design was often the basis for many other vehicles. By the end of the war, and the consolidation of the various dispersed Armor branches brought under the new Armor branch, the M4 Tompkins in its various forms would comprise the majority of armored fighting vehicles for the United States and many of her allies for the next two decades.
The M4 Tompkins carried the US 75mm L/47 Tank Gun, M7. An extended high velocity version of the already effective 75mm M3, designers were tasked with creating an effective anti-armor weapon at a cost of infantry support (which was still the purview of the ‘infantry’ tank class when proposals were sought). The creation of the 75mm M7 was directly tied to the M4 Tompkins development, since the increased size of the weapon meant the need for a larger space to accommodate the greater rearward travel of the gun after firing.
The gun barrel measures 11 ft 5.5 in (3.5 m) long and marginally thicker than the previous iterations of the venerable 75mm tank gun. Early test versions of the M7 didn’t incorporate a muzzle brake, this was found to stress the recoil mechanisms on test platforms and muzzlebrake was added. The addition also helped to reduce the flash of unspent powder which tend to momentarily blind the gunner and commander.
While it originally was based on a field gun, the M7’s development to a more dedicated anti-armor weapon came at a price of its reduced anti-infantry effectiveness. While it carried high explosive rounds and some canister and specialized rounds, the majority of its official load are of AP and AP-Capped shells. By the end of the war though with the reduced dependence on the ‘infantry’ tanks by commanders, efforts were underway to adapt a HE shell that could be just as effective as the weapon the M6 Sherman utilized. In the interim, more and more tankers in the field started to carry more HE shells, even if it would cause some problems with loading.
The weapon fired a reduced-charge HE shell that was primarily used against light fortifications and lightly armored vehicles and infantry, while on paper four to six rounds were reserved for canister and smoke and white phosphorous rounds. Canister rounds were more liked (and used) by the Armor forces of the US Marines and US Dragoon units fighting in the Pacific Theater. In practice, the majority of the rounds were of the standard Armor Piercing and later, the improved Armor Piercing-Capped.
A major improvement over the M2 McGilvery was the gun-handling mechanisms found on the M4 Tompkins. It featured a gyrostabilization unit for the gun and gunsights. While in practice it wouldn’t be useful on fire on the move, it helped keep the gun relatively on target during movement, allowing for faster acquisition when stopping. The gunner had both a periscopic sight and direct vision gunsight. Originally of fixed magnification, the gunsight was later upgraded in 1943 to be a variable magnification sight. The turret is electrically powered, with traverse and elevation controls being easily switched from powered to unpowered modes.
As the war continued and a further blurring of the line between ‘infantry’ and ‘cruiser’ tanks occurred, a design program looked at dropping the 75mm M3 Tank Gun into the Tompkins turret. The resulting M4 (Short 75) project was the death knell to the ‘infantry’ tank concept as the army became more and more mechanized and ‘infantry’ tanks were left to be used as tactical reserves in semi-static defenses and spearheads into fortified areas. These Short 75 Tompkins were popular with regular infantry forces due to the increased infantry support capabilities even if anti-tank performance was lacking.
Other weapons considered were modified 75mm Pack Howitzer M1s or 105mm M2A1 Howitzers in close support roles. Eventually the heaviest weapon that was to be fitted onto the M4 Tompkins was the 90mm L/53 Gun M3, though not without needing a completely new turret and beefing up of the recoil mechanisms and the need for a large “U shaped” counterweight that extended the already elongated turret over the engine deck and reducing space inside the turret.
Other than the main gun, most iterations of the M4 Tompkins carried the venerable M1919A5 .30cal Machine Gun in a coaxial mount, and the M2HB .50cal Machine Gun on a pintle on the commander’s cupola. When close support versions of the Tompkins was trialed, some were given an experimental coaxial mount that mounted the M2HB .50cal, and a semi-open turret that allowed the mounting of four M2HB .50 cal Machine Guns or two 25mm Autocannons for anti-aircraft and direct fire roles.
And that was it…I’ve yet to tackle armor (need to have a 5minute rundown on metallurgy and the like for it), engines and transmission, crew comforts, and the like. I also aimed to do an in-depth ‘walk-around’ of the tank similar to The_Chieftain’s Inside the Chieftain’s Hatch videos…and I’m cross-posting this on Facebook.