Today we are going to take a look at the current American tech tree, specifically the current medium branch at the top, tier 9 and 10. Has it been power creeped to death? There will be three total articles covering briefly the development of post war American medium tanks to the early 1960’s. The time line for most high tier tanks from tier 8 to 10. Then the third and final article covering possible solutions for the American medium tree and its spot currently in World of Tanks.
M46 Patton: MORE POWER!
The planning for a new medium tank all started in June 1945, a report given by the Equipment Review Board in Washington D.C. suggested that from the results of tank on tank engagements of WWII there needs to be development of a light, medium and heavy tank each with a set weight limit (23,45, and 75 tons). For the medium tank it was desired to have adequate protection against most modern tank weapons with 8” (203mm) of frontal armor and 3” (76mm) on the side. It would have decent mobility with the appropriate power package, and also mount a weapon capable of knocking out most known armored vehicles of the day.(see  pg.7)
Fast forward to 1948 and the order of 10 new medium tank T40’s. These were modernized and improved version of the under powered M26 Pershing. They were given an AV-1790-3 engine putting out 810 gross horsepower (up from the 500hp Ford engine in the Pershing) and a new transmission. This program would result in improved mobility for the modified M26 hull’s used in the test. This development would be noted on the Ordnance Technical Committee Minutes (OTCM) on 30 July 1948 as the standard for the modernized Pershing and deemed the new vehicle as medium tank M46. (see  pg.14)
|Cross sections of the M26 top, and the M46 bottom|
Medium tank T42: The tank with a little heart
Note that nowhere was there mention of an upgraded armament for the M46, the engine and transmission were the major upgrades. Now for this we have to go back a bit to December 1948 that after several months of features being thought up for a new Medium tank to replace the Pershing. Thus a new tank was designated, the medium tank T42. This new design had to weigh about 36 tons and offer better protection than the current M46. This would retain the same fire power mounting a 90mm gun as the previous tanks. Objections by a British liaison about the power of the 90mm M3 compared to the 20-pounder gun spurred the development of a new gun however: 90mm gun T119, and was required to penetrate 11.1”(281.94mm) of armor at 30 degrees at a range of 1000 yards (914.4m). To conserve weight, it was requested to use a new light tank power package: a Continental AOS-895 gasoline engine putting out 500hp. This setup would be deemed underpowered in June 1950 though, but with the hope of the T42 being a lighter and more economical medium tank then the M26 and M46 development continued. The result of the original power package being underpowered lead to the development of AOS-895-3 engine and a refined transmission being placed in, and resulted in it being roughly 500lbs lighter. This new power package did meet the OTCM specifications, however it was still considered by the Army Field Forces to be underpowered. By then the US Military's focus was on other tank projects and the project started to stall.
The T42 project would continue for a bit longer but by May 1953 the program was almost at a complete dead end and by October 1954 was officially canceled. Though the T42 did continue serving in other projects, the hull being used in the T69 program and the turret was tested on the M46 hull. During the life of the T42 project as well there was small but important action taken by the Army Equipment Development Board, this was reclassifying how the tanks would be designated. Instead of their weight as the determining factor it would be by the gun that was mounted on the tank, Lights with 76mm guns, Mediums with 90mm, and Heavy’s with a 120mm. ( pg.32-47)
M47: Briefly around
With the T42 program stalling out by mid 1950 there was still the issue of getting a new tank for the US military. With the Korean war in full swing and the military in dire need for a new medium tank. The idea was thought to place the T42 turret with the new T119 gun on an existing M46 hull this was designated the medium tank M46E1 and testing began March 1951. There was also further need to improve the M46 hull with increased protection by thickening the frontal armor and increase the angles for each glacis, as well some modifications for fitting the T42 turret. The result of the M46E1 with the improved hull would be designated M47. Through this whole time from the M46 to the M47 there has not been a mention of any high velocity 105mm gun mounted or planned to be placed in any M46,T42, or M47! At least not with the US military... The M47 would be short lived within the US military with its production ending in 1953 and the plant switched to a new design. The M47 would still continue to serve in other nations for several more decades. While serving in other militaries they would receive upgrades and modifications several times throughout their service life, including mounting the 105mm L7 and/or the engine and transmission from the M60, as well as improved FCS.(see  pg.52-pg.75)
M48 Patton: Almost. . .
In the summer of 1950 there was already knowledge among a majority of Ordinance recognizing that the M47 was going to be a tank that would be briefly produced, a “stop gap” if you will. To quote here “Parallel with the approval of the M47 production, a maximum effort began to design its successor, The new tank was powered by the same engine and transmission of the M47” - Hunnicutt pg. 83. Come November 1950 the new design was in drawn up concepts and given to the Chrysler’s Ordnance Development Department and by February 1951 the project is given the name 90mm gun tank T48. Armed with a new lighter weight 90mm that offered the same performance as the previous 90mm, this new gun would be designated 90mm gun T139. Given a few years of development come 2 April, 1953 and an OTCM standardized the new tank as 90mm gun tank M48 armed with 90mm gun M41.
Initially, the M48 was produced by two different manufacturers, each resulting in a slightly different tank. The M48 had a commander's cupola with a pintle mounted .50 cal that was a more standard hatch design, this variant also had a smaller drivers hatch. The other was the M48A1 that had a larger drivers hatch and an larger commander's cupola with a M2 .50 cal mounted internally. There would be an upgrade program to update the production M48, this new upgrade package included a new fuel injection model of the current engine along with modified transmission as. There was an updated hydraulic package for the turret and gun controls as well. The resulting new vehicle would be the 90mm gun tank M48A2. Production of M48’s would only last until 1959 after a new improved tank design was chosen. The tank would continue to serve the US military and foreign users for several more decades. Receiving many upgrades and modifications within its service life up till the mid 1990’s with in US reserve units and can still be found in some militaries today.( pg 83-pg.122)
Medium tank T54: Up gunned!
In December 1950 an Army Equipment Development Guide would suggest that a development of a 105mm armed tank begin, feeling the future of armored vehicles would require such firepower and was even considered during the T48 testing, finding out there was enough room in the turret to accommodate the larger weapon. This would lead to on July 6th, 1951 the start of such a program. Built on the M48 chassis and wielding the 105mm gun T140 with an autoloading mechanism, two designs were developed under the project designation T54.105mm gun tank T54 tested an autoloading mechanism, based on an earlier 90mm design for the M48, that would be capable of selecting between three types of ammunition. Whereas its partner T54E1 would be testing the gun in a comparatively more ordinary oscillating turret configuration. .
|T54 left T54E1 right|
Moving to late 1952 there was a study to cut cost and simplify the turret of the T54. On 18 May 1953 the 105mm gun tank T54E2 was designated. This variant had no automatic loading system and resulted in a lighter weight turret along with simpler operations. With the new T54E2 as well was a new gun the 105mm T140E3 this was mounted in the new turret. The big advantage of the new turret was a new gun mount as well for the T140, this had a shorter recoil distance travelled by the breech to only about 10”, this being 2 to 4” less than other 105mm gun and even current 90mm currently in the M48. This turret could be installed on a Standard M48 hull with only a few modifications being in the ammo stowage in the hull to store a total of 39 105mm rounds. For all the T54 program offered it was terminated by the Ordnance Committee in January 1957, but the program would continue to contribute to others for a few more years to come...(see  pg.126 -pg.142)
 Hunnicutt, R. (1984). Patton: A history of the American main battle tank. Novato, Calif.: Presidio Press.