Why no sherman 90mm

[roqf77]

the firefly improved allied v german heavy tank relations, as far as i know the 17 pounder is of similar size to the american 90mm and similar power and ammo of similar size. This makes me think why did the us not produce 90mm armed shermans?

it would of imroved the firepower of us tank divisions they certainly would of been able to produce enough to make a significant improvement.

Was there any practical reason for this if not why did it not happen, i know attempts to factory produce fireflys in the us failed so they would of least of been made aware of the idea if they were not already.

[Kingfish]

Originally posted by roqf77:

the firefly improved allied v german heavy tank relations

Actually, the 'fly put a damper on allied German tank relations. Before the 'fly came along the German tanks were very happy to see the allied tanks, and wished to see more of them. Everyday. But once the 'fly appeared the Germans weren't so thrilled. Sad really.

[flamingknives]

Recoil travel? There's only so much room behind the gun in a sherman turret.

The 90mm gun was produced on a Sherman chassis in the form of the M36 Jackson tank destroyer. This had a much lighter open-topped turret.

The 17pr gun was pushing the limits of the Sherman turret as it was, and you cannot simply put a larger turret on a tank, as the extra weight will overstress the suspension units, limiting mobility, or overload the traverse mechanism, making it more prone to failure.

It was my understanding that the US never tried to make the 17pr. gun integral to the Firefly, as they had their own 3" gun in development/production and the 90mm on the horizon.

[roqf77]

freespace.virgin.net/shermanic.firefly/home1.htm

here is a website with information on the firefly in us service. not the first one i found but i cant find that one now. although it seems they were never used.

[PJungnitsch]

No problem with the Sherman itself, it's a big tank compared with the PzIV and had a much larger turret ring. The problem was that there were too many factions that controlled US tank development and they tended to deadlock each other, that and a lot of ideas were floating around that were simply wrong.

Some fought 90mm Shermans on the basis that the 90mm should only go to properly designed new tanks (the Pershing, who's development ended up taking to long for the war). Others fought 90mm Shermans on the basis that tanks shouldn't fight tanks, and the 90mm would just encourage that. Then there was the idea that the 76mm would be loads of gun to fight whatever the Germans had.

[YankeeDog]

While I agree with all the comments about US tank deveopment, I'm really not convinced it was technically feasible it was to put the 90mm gun into a Sherman.

The Brits had to go to great lengths to fit the 17 pdr into the Firefly. While I don't have the techincal specs immediately handy, IIRC the 90mm is heavier and bigger than the 17pdr.

While the US arms establishment certainly initially thought the 76mm would be plenty of gun for their tanks in the early and mid-war, by late war, the US arms establishment was well aware of the need for 90mm platforms -- hence the stopgap measure of the Jackson, and the rushing of the Pershing into service before it was really ready. If they could have just slapped a 90mm into a Sherman, I bet they would have. There were plenty of 90mm guns around -- quite a few had been manufactured for heavy AA, a function for which they weren't really needed by 1944.

The US army continued to use the Sherman right through Korea, and AFAIK never upgunned it to larger than 76mm. This alone makes me suspect that there were technical problems with this chassis-gun marriage.

Cheers,

YD

[flamingknives]

The Isrealis did upgun the Sherman with a British 105mm gun, but that's a whole different kettle of fish compared to WWII cannon. Plus the tank itself has a new turret and the very latest suspension. No idea what the armour was like though.

[YankeeDog]

That's right. I forgot about the Israeli 105mm Shermans.

As you note, though, there's some pretty big changes to the turret and suspension in that design, and the gun (and presumably recoil mechanisms as well) is also much more advanced. I'd be curious to see the engineering behind that combo.

From the US's prespective, though, at the point they realized a 90mm gun platform was really needed (maybe early 1944 or so?), if it would have required a complete turret and suspension redesign to shoehorn a 90mm into a Sherman, they were probably better off just continuing with the T-26 program and fielding 90mm guns that way, especially since the T-26 program was already pretty far along at that point -- IIRC, as it turned out, it was unanticipated problems with the engine and drivetrain that delayed the Perhing's deployment, not lack of a completed design.

Probably the biggest mistake was putting the T-26 program on the back burner in 1941 & 1942 because they didn't think such a "heavy" tank would be necessary. Without that delay, the US Army probably would have had working Pershingsk presumably with 90mm guns, much earlier, perhaps even hitting the beach on D-Day.

Cheers,

YD

[John D Salt]

Originally posted by YankeeDog:

While I agree with all the comments about US tank deveopment, I'm really not convinced it was technically feasible it was to put the 90mm gun into a Sherman.

The following methods were tried:

1. A study by BRL (Aberdeen) dated 31 Oct 1942 concluded that the 90mm could be mounted in the M4 turret, but would require the gun to be modified to provide a recoil slide surface outside the turret, and, because of the difficulty og handling such long rounds, probably have the cartridge case reduced in length (in turn reducing propellant contect and projectile velocity). A picture of a proposed 90mm Sherman, with VVSS and the hull sihouette lowered, appears on p. 212 of Hunnicutt's "Sherman". The study also proposed a high-velocity (3,000 ft/sec m.v.) 75mm weapon. In Autumn 1943 the Armored Board wanted 1,000 90mm-armed M4A3s available in time for D-Day, but the Ordnance Board insisted that Pershing was the right answer and Army Ground Forces said that it was not tanks' job to kill other tanks.

2. In the latter half of 1944, Detroit arsenal had an M4 fitted with a T26 Pershing turret (easy to do as both tanks had 69-in turret rings). This used VVSS production, but HVSS would presumably have been used had production been ordered; a drawing of such a vehicle is on p. 213 of Hunnicutt's "Sherman". This would have taken 6 months to make "production quantities" available. It was decided to wait for Pershing.

3. The M36 tank destroyer was standardised in July 1944, and in October 1944 the M36B1, produced by mounting an M36 turret on an M4A3 chassis, was declared substitute standard.

So I think there are at least three techically feasible ways of getting 90mm armament into a Sherman.

All the best,

John.

[YankeeDog]

Thanks for the info, John. I guess a 90mm Sherman would have been feasible, at least from a technical standpoint.

But option 1 isn't really the same, since it would be a reduced-velocity 90mm. Still, it might have been a good idea, as I imagine a moderately reduced velocity 90mm would still be substantially more effective than the 75mm, and quite probably the 76mm as well (and presumably improved HE blast, too).

By my math, option #2, and depending a bit on exactly what "latter half of 1944" is, this doesn't get the 90mm Shermans to the front lines a significant amount earlier than the Pershings, so there doesn't seem to be much point.

And of course, option #3 was actually done. . .

Cheers,

YD

[dalem]

They also tried the 90mm in the M36 turret on the M-18 Hellcat chassis. It worked just fine but overstressed the suspension and tracks when firing off to the side so was not seen as viable.

-dale