Super Pershing and Persherman for 1944 US Army

JWilly

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Regarding AFV designs and utilization, the US Army during WWII of course focused on manufacturing economies and rail/cross-Atlantic transportability, and (at least through mid-1943) convinced itself that the Sherman was good enough against German armor; that its 75mm HE efficiency outweighed any AP limitations; and that it was the job of lightly armored tank destroyers, not tanks, to fight other tanks.

Especially from mid-1943 onward, the shortcomings of this analysis were recognized in some quarters. Shermans evolved toward 76mm guns mounted in more spacious T23 turrets, some Jumbos were fielded, and 76mm HVAP ammo became more commonly available. But, the original concepts by and large had considerable institutional momentum. The M26's arrival at the very end of the war was the beginning of the next generation, but WWII was essentially won by then. Fortunately for USA, the next generation of German tanks could not be fielded in significant numbers, and USA did not have to fight the Soviet Union's late-war tanks that did exist in larger numbers.

The M26's design was compromised by use of available subsystems per that manufacturing-economy focus, resulting in it having too little mobility. The Sherman and Sherman-like-TD experience with 75mm/76mm guns had shown that caliber class to be able to be optimized for either soft or hard targets, but not both. And, the medium-length 90mm M3 gun, even using HVAP ammo, was only adequate for engaging first-tier enemy tanks out to moderate ranges.

What if the US Army's collective thinking from 1943 onward had instead concluded that greater combat effectiveness should move up in the priority-stack as soon as possible...meaning that every front line tank (not counting scouts etc.) should be capable of engaging soft targets with maximum effectiveness and engaging other tanks when present?

The Army of course was structured with armor-supported infantry divisions for most sectors, and armored divisions for special tasks. The infantry divisions' tanks only required moderate mobility per their doctrinal tasks, and could rely on HVAP for engaging other tanks as long as the infantry tanks had at least 90mm medium-length guns. The armored divisions' tanks needed more gun capability and greater mobility.

The Sherman utilized the same turret ring diameter and drive systems as the M26. It was possible, without significant changes, to mount the T26 turret with 90mm M3 gun, as used on the M26, to a Sherman chassis. (Of course, ammo racks had to be changed and the standard load became smaller.) This combination was prototyped in 1944 by Chrysler, who were unable to convince the Army tank bureaucracy that its increased combat effectiveness would outweigh the systemic complexities of implementing such a change. The design was known as the "Persherman".

wvl0tu1v6eg41.jpg


In this alternate proposal, this would have been adopted in late 1943 or early 1944 as the standard infantry-support tank. Existing US Army Shermans with low enough wear would have been field converted, using T26 turret/gun subsystems and new ammo-rack kits shipped to Europe. Production of all the TD versions for US use could have ceased, with all new US-use Shermans going to Europe already built as Pershermans. Because the T26E3's never-fully-resolved running gear and powerplant development issues would not have been in the way, this could have gotten 90mm tanks into the field many months ahead of when the T26E3 (which became the M26) finally reached Europe.

In this alternate proposal, the standard armored-division tank would have become the Super Pershing, with the gun and gun mount of the T26E4 (L/73 T15E2 90mm gun, two piece ammo, no external stabilizer springs required) and with the improved powerplant and suspension of the M26E2...those different design choices having been technically straightforward during WWII, but not implemented because of the same "manufacturing economy" thinking. The Super Pershing would have taken longer than the Persherman to field due to its greater number of technical developments, but it still could have been been fielded sooner than the historical T26E3 (M26) if per our alternate proposal, the infighting between Army Ground Forces, Armored Force and Ordnance had been much earlier resolved in favor of 90mm guns and greater tank combat capabilities.

Super Pershing with external stabilizer springs:

maxresdefault.jpg

Super Pershing without external stabilizer springs:
T26E4-prod..jpg

(edited 6/3/2023 to fix dead image links)
 
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It might be better to move this thread to the Alternate History section.

That said: the US could definitely have future-proofed its AT more, as the British and Soviets did. There were some major issues with the way information was spread that meant that US field commanders were never informed of what was in the works and could interest them, and info from one theater was not spread to another. This is why the ETO commanders were dismissive of the 76mm Sherman even though the troops in Italy on the other hand requested ONLY 76 when they got some.

The medium length 90mm already existed even before 1940 and was replacing the 3" AA, while the barrel and case of the 3" AT gun were actually prototypes that were never produced. Thus even from the standpoint of using existing production capacity the 3" was actually a worse option than the 90mm! The Soviets who faced the same situation with the 85mm replacing the 76 for AA decided to drop the 76mm long tank gun to develop a 85mm instead (1940-41).

The Americans apparently still preferred to develop 3" guns, even in 1944, probably because they could carry more rounds (and dismissed the greater payload of 90mm HE that could make up for lower ammo capacity). Even then, they were quite below the curve as the 3" M7 was so overbuilt (parts specced to even use 17pdr barrels and ammo, ridiculously underfilled propellant case) that it could be turned into a 3000 fps muzzle velocity weapon, instead of 2600 fps, with relatively little work. This was suggested by Canada. The other option would be to actually use the 17pdr ammo and barrel, which might yield a better design than the real 17pdr itself or at least would be far easier to integrate in the M10 for example than the British 17pdr for the Achilles conversion. Once again, all this could be done before M10 even enters service. Finally, one could also have taken the more modern 90mm design and reworked it for 3", yielding a more efficient high velocity 3".​

M10 was also modified to use the 90mm, where this wasn't any worse than the 3" outside of needing slightly heavier counterweights, so that conversion could have yielded pseudo-M36ses months in advance.

Another moment when the US could have been faster, is to specify a 90mm T2X prototype at the same time as all the other protos (with 3" M7, 75mm, 76mm M1). The turret design was derived from 76mm versions anyway so this would effectively have greatly accelerated development of the 90mm turret and tank. Since it would have to be heavier anyway, it would also show the need for reinforced parts early. In general this would have greatly accelerated development of the T25/T26. This solves the main issue of the historical M26, that it was kinda added late to the T2X family (mid/late 43 instead of mid-late 42) rather than being worked on at a normal pace. This would also give the opportunity to increase turret ring diameter once again to 73" or so to better handle the 90mm, as was done on the same hull family with M47. The long 90mm could have started earlier at the same time as the British 32pdr if you really want it.

Another fix would be to just go with the Ford V12 instead of turning it into a V8 for tanks. The V8 ended up never being used for light tanks and tank destroyers or support vehicles anyway, the T2X family was designed from scratch so could handle the V12 anyway, and the Sherman could handle the V12 as long as it was stretched like the A4. The transmission could handle 550hp or so so when accounting for power losses to cooling and other accessories, so a derated V12 with 600-700 horsepower could be used while the 500hp V8 was still underusing the full capacity of the transmission.

Persherman itself could happen in an organic way if the US opts for more powerful guns than the 2600 fps 76 anyway.
 
Another fix would be to just go with the Ford V12 instead of turning it into a V8 for tanks. The V8 ended up never being used for light tanks and tank destroyers or support vehicles anyway, the T2X family was designed from scratch so could handle the V12 anyway, and the Sherman could handle the V12 as long as it was stretched like the A4. The transmission could handle 550hp or so so when accounting for power losses to cooling and other accessories, so a derated V12 with 600-700 horsepower could be used while the 500hp V8 was still underusing the full capacity of the transmission.

Was the GAC or one of its predecessors ever actually mounted in an M4A4? Would love to hear more about this if so.

Also, does anyone know if there was a reason why a modified M36 turret was never considered? Could a coaxial MG and roof not be added to the turret on an M36B1-esque design?
 
Another fix would be to just go with the Ford V12 instead of turning it into a V8 for tanks. The V8 ended up never being used for light tanks and tank destroyers or support vehicles anyway, the T2X family was designed from scratch so could handle the V12 anyway, and the Sherman could handle the V12 as long as it was stretched like the A4. The transmission could handle 550hp or so so when accounting for power losses to cooling and other accessories, so a derated V12 with 600-700 horsepower could be used while the 500hp V8 was still underusing the full capacity of the transmission.

Was the GAC or one of its predecessors ever actually mounted in an M4A4? Would love to hear more about this if so.

Also, does anyone know if there was a reason why a modified M36 turret was never considered? Could a coaxial MG and roof not be added to the turret on an M36B1-esque design?
It appears that the GAC testbed never happened no.

I would now add after more research that the V8, being based on the V12 had a 60° bank angle, which is not ideal for just 8 cylinders. This probably contributed in part to the technical problems of the engine at the time, plus other maladaptations of the engine to the new cylinder count. In hindsight keeping the V12 might have allowed development to be completed sooner with a more reliable engine with greater potential.
That said, it appears that cooling was a greater bottleneck than the transmission in the Sherman, knowing that the Chrysler A57 was derated for this reason. But regardless the Americans needed to work more on the cooling and transmission in the future so making that more necessary would always be good.

M36B1 was an unintended design and the T23/T26 turret was more suitable for an enclosed turret with a coax and the 90mm anyway, so it made little sense other than expediency to develop a M36 turret with a coax and roof.
 

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