WW2 British Prototypes WW2 US Heavy Tank Prototypes

Heavy/Assault Tank T14

United States of America/United Kingdom (1942)
Experimental Heavy/Assault Tank – 2 Built

At the meeting of the Joint British Tank Mission and United States Tank Committee in early 1942, the question of designing a medium heavy tank or assault tank was discussed. It was stated that the US had no requirement for such a vehicle, but that the UK had an urgent need. It was agreed that the US should develop and manufacture two assault tank pilots based on the M4 Medium whilst the UK would develop and manufacture two assault tank pilots based on the A.27 Cromwell. This vehicle would become A.33 Assault Tank, often known as “Excelsior”. One of each of these pilots would be interchanged and tested concurrently in the two countries. It was also established that the eventual production requirement would be for 8500 vehicles.

The US Tank Mission established the required characteristics for their model at a conference on the 30th of March 1942. The Aberdeen Proving Ground was instructed to proceed with initial drawings and to build a wooden mock-up. In May 1942, the Ordnance Committee designated the project T14. By June, APG had finished the preliminary drawings based on an all welded construction.
It was not the first time the two countries had worked on a single tank design for both armies to use. They had previously worked on the Mk.VIII “International Liberty” in 1918, towards the end of WWI.
One of the T14 prototypes. Note the extreme angle of the frontal armor.
One of the T14 prototypes. Note the extreme angle of the frontal armor.

Dough Boy meets the Tommy

The T14 started life as the first Churchills began rolling off of the assembly line. At the time, the British Infantry Tank was a less than reliable vehicle, to say the least. As such, the T14 was designed to be somewhat of a replacement for the Churchill and was meant to be faster, better armed, and also better armored. The Americans would also see it as an upgrade to their M4 Sherman Medium Tank. The wooden mock-up was shipped from APG in July 1942 and two prototypes were ordered for testing from the American Locomotive Company. The tank was designed to share as many parts as possible with the M4. In fact, the armor thickness of the frontal plate was the same as the M4, 2” (50mm) but sloped at a steeper angle of 60 degrees, increasing the effective line of sight armor thickness to 5” (127mm). The turret was 4” (101mm) thick on the sides and rear and 3″ (76.2mm) on the front, with the front partially sloped at 30 degrees. It had the added armor of the mantlet, which also came from the M4. Armor on the flanks of the vehicle was 2 ½” (60 mm) steeply sloped again at 60 degrees, with another 2” (50mm) on the rear. The running gear was protected by hinged armoured side skirts, or “Bazooka Plates”, that were ½” (12.7mm) to add protection for the running gear and lower hull from high explosive rounds.
Preliminary design studies were made for a leaf type of suspension, but it was decided to use the suspension designed for the M6 Heavy Tank. It consisted of a double set of road wheel bogies (inner and outer) using a horizontal volute spring and a 25 ¾” (654mm) track as the facilities already existed for production.
Initial designs allowed for a Ford GAZ V8 with a provision for a later installment of a Ford V12 unit. The 205-gallon fuel tanks should have provided a 100-mile range with a maximum speed of 24 mph on road. A maximum gradient climb of 60% was achieved with a vertical obstacle clearance of 24” (609mm), a trench crossing ability or 9’ (2743mm), and a fording depth of 36” (914mm).

A shot of the T14 at Aberdeen. If it looks strange, it is because we are looking at an early form of Photoshop. For whatever reason, APG occasionally painted over some of their photos. On this image, both the foliage on the right and the gun barrel are drawn.


The T14 was designed with the option to carry either the American 75mm Gun M3, the same gun found on the M3 Lee/Grant Medium Tank and early models of the M4, or the British QF 6-Pounder Gun found on the Churchill and Crusader. At the time of design, these guns were capable weapons, able to deal with the German Panzer IIIs and IVs. The 75 mm gun could penetrate 76 mm of armour at 1000 m. The 6-Pounder was slightly worse, with 66 mm of penetration at the same distance. As said, these were capable weapons at the time of the tanks initial conception. However, the changing nature of the war would mean larger guns were needed, but the small turret did not leave much room for future upgrades.
In July 1942, APG was requested to make a study of the layout drawings for mounting a 105 mm howitzer in the tank and consideration was made for possible 76mm and 90mm upgrades. Defensive armament consisted of 2 Browning M1919 A4.30 cal machine guns, one mounted in the hull, the other coaxial. It also carried a roof mounted M2HB .50 cal machine gun but this was quickly eliminated in favor of another .30 cal M1919A4.
Ammunition stowage was for 90 rounds of 75 mm, 9000 rounds of .30 cal and 600 rounds of .45 cal for close crew protection (presumably a Thompson SMG).

The T14 on the testing grounds at Aberdeen. Photo: – Don Moriarty


Difficulties in procuring materials for the prototypes was encountered because of a low priority rating that was already applied to the project but a higher rating was obtained in August 1942. By June 1943, the first pilot was complete and delivered to APG for testing in July and the second the following month. During testing, a number of small mechanical modifications were made and some of these were incorporated during the build of the second pilot. The testing was terminated early before completion on the 4th December 1943, due to another downgrading of the project’s priority. At this point, the second pilot was shipped to the UK. The report made after the British trials was pretty damning.
Some of the problems highlighted in the report are listed below:
‘Since the only irregularity on the hull front which would trap a projectile is the bow machine gun port, consideration should be given to its modification or elimination’
‘It is difficult to adjust the tracks on this vehicle because of the weight of the tracks and the location of the inside adjusting mechanism’
‘The bogie wheels, especially the outside centre set are constantly badly damaged by the tracks when operating over cross country terrain, in turn, the track guides are broken and the nuts and wedges lost’
‘When operating over hilly cross country terrain the tracks are thrown frequently, especially on side slopes’
‘The entire suspension system is not satisfactory and should be improved or if possible replaced’
‘For better protection, the ammunition should be removed from the sponsons and placed below the sponson level’

Following this, these recommendations for the T14 were made:
a) The Assault Tank T14 be given no further consideration in its present stage of development.
b) If further consideration is given to this vehicle, the modifications in the above conclusion, be incorporated and the vehicle should have been subject to further tests.
This effectively killed the project as the British came to the same conclusions when they tested the second pilot vehicle. The project was officially canceled on December 14th, 1944. The first pilot that remained in the US was scrapped and the second pilot in the UK eventually found a home at The Tank Museum, Bovington. It can be found today in the Vehicle Conservation Centre.

An article by Mark Nash and Adam Pawley
The T14 in Bovington's Vehicle Conservation Center - Photo: The Sherman Tank Site
The T14 in Bovington’s Vehicle Conservation Center – Photo: The Sherman Tank Site

T14 Heavy Tank specifications

Dimensions (L-W-H) 6.20 x 3.20 x 3.00 m (20.34 x 10.50 x 9.84 ft)
Crew 5 (driver, gunner, loader, commander, bow gunner)
Propulsion 520 hp Ford GAZ V8
Speed (road) 24 mph (38.6 km/h)
Armament 75 mm Tank Gun M3
2x Browning M1919 .30 machine guns
Browning M2HB .50 machine gun
Armor 50-101 mm
Total production 2 Prototypes

Links & Resources

The T14 on Military Factory
Aberdeen Proving Ground, Maryland, First Report on Assault Tank T14 and First Report on Ordnance Program No. 5621, Febuary 28th 1944. Readable copy can be found HERE.
Bovington Archive Library: British/American Evaluation of the T14
Osprey Publishing, American Tanks & AFVs of World War II, Michael Green.
Presidio Press, Sherman – A History of the American Medium Tank, R.P. Hunnicutt

The T14 heavy tank - Illustrated by Jaroslaw Janas
Tanks Encyclopedia’s own rendition of The T14 heavy tank – Illustrated by Jaroslaw Janas

By Mark Nash

Member since 2016. Specializes in weird. 120 articles & counting...

16 replies on “Heavy/Assault Tank T14”

how do they remove the radiation hazard, if they restored it in protective clothing, why would it matter, it could be cleaned afterwards…

Radium contamination, not tritium. Tritium is a hydrogen isotope with a 12 year half life. It would be all but gone now, except for very trade amounts and if a tritium vial leaks it disappears quickly. Radium dust on the other hand is what killed a crap ton of watch makers and Marie Curie. It is a heavy metal and decomposes into radon gas when it emits an alpha particle. Radium is actually more radioactive than U-238 pound per pound.

I mean, it has the shermans suspension its just a different hull but the turret is about the same

I mean like if you look closely at the front plate on the hull, it kinda looks like the front of the M4 Sherman so in a way yes it kinda is a beefed up M4.

Have you guys ever hear of the M4A3E8 Thunderbolt VII? It would be cool if you would do a article on it. Its kinda like a T26E4 and Easy Eight hybrid.

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