US tank design and philosophy

[R011]

40 minutes ago, futon said:

Well to your bottom point, the Pershing turret M4 probably still be considered a "Sherman". It would be in consideration as to whether to introduce the whole M26 was the way to go. So on your point, instead of sending a few M26s to Europe to test it, it would make more sense to go with the M26's turret on M4 -- on the basis that this design passes all testing. Doing so reduces risk to logistics. M4 hull parts, training, familarity was already in system. 

If the M26 had a better engine, then maybe it would cross the threshold of substantially better. But it was pretty much the same engine as M4. Both were working with same engine power. 

With all that said, if hell broke out with Operation Downfall.. the 90mm would actually be overkill for most things. And slower M26 speed wouldn't be an issue with the type of warfare that would have occured. It would be more of the same kind of slow close quarters fighting like it was on Peleliu, Iwo Jima, Okinawa.. the tank crews would likely greatly appreciate the M26's front and side hull armor. If no M26s, they'd probably want 75mm or short 105mm armed Jumbos over Pershing turreted M4s.

They could spend a few months designing an actual Pershing Turret Sherman, or they could just make Pershings which were then ready for production.

[DogDodger]

ETO refused to accept a tank that stowed less than 70 main gun rounds, which is a big part of the modifications involved going from T26E1 to T26E3. Wet stowage was even dropped. M36 only managed forty-seven 90 mm rounds. Despite the Armored Command's enthusiasm, a 90 mm medium tank based on the M4 was not going to happen.

[Manic Moran]

It's also worth noting that when it was determined that it wasn't particularly difficult to replace the 76mm on M18 with the 90mm turret, the report observed that the 76mm seemed to be doing pretty well as it was, and pulling vehicles for conversion would probably have been less effective than just leaving them overseas.

Just on the matter of the M4 with the 90.

That was the trump argument. There were other arguments, such that the M4 with the 90mm turret did not meet ETO requirements for mobility.

From 

For the flak McNair gets, I think it's unjustified, I've seen very little in the archives to support he was particularly detrimental to armor development. As Charles Bailey pointed out in 1977, McNair makes a great scapegoat for Ordnance historians, helped by the fact that he was dead and couldn't defend himself.

I have my own video covering McNair's influence (Not exclusively on it, but he features heavily).

 

 

[DKTanker]

Seems that there was a whole raft of actors suffering from the same malady, lack of aforethought. 

Example:  90mm gun construction was the bottleneck is often the argument heard.  What isn't usually noted and queried is that 90mm gun construction was completely halted and apparently the project shelved or even scrapped thus necessitating the entire project being rebirthed from the beginning.

Example:  The original 75mm gun for the M4 was shortened by 8 calibers because the original length inhibited mobility (it stuck out too far).  That's the same argument that was being made about installing first the 76mm and then the 90mm had it been available.

Example:  It would be more than eight months after the M4 was accepted for production that a follow on project was initiated.  People with aforethought would have initiated a new program even before the M4 had been accepted.

Example:  Gun and ammunition design stagnated.  Not until 1959 with the acceptance of the L7/M68 as the tank gun of choice did the US Army realize that a shouldered cannon round, that reduced the length of the cartridge, was even possible.

[bojan]

20 minutes ago, DKTanker said:

...

Example:  The original 75mm gun for the M4 was shortened by 8 calibers because the original length inhibited mobility (it stuck out too far)...

Since it used same same ammo ballistic loss was probably minimal.

Soviet 76mm L/40 (ZiS-3, F-34, ZiS-5) and L/50 (F-22) differed in less than 10% penetration, since both used same ammo, which was originally designed for L/40 guns. This is pretty good analogue to the situation with original Sherman's gun, since  Soviet 76mm and US 75mm used somewhat hotter charge in the cartridge case from a WW1 field gun.

Also, it was not only US that had "gun should not stick too far" logic, Soviets originally put L/32 gun into KV instead of originally planned L/51 since it did not exceed hull dimensions. British also insisted on that until late 1942. at least, as did Germans early on, with 50mm L/42 that was choses over 50mm L/60 for same reason, and also insisted on rear engine - front transmission layout for exactly same reason.

In hindsight they were ofc all wrong, but it is unfair to single out US tank designers for that fault.

  

20 minutes ago, DKTanker said:

...Example:  Gun and ammunition design stagnated.  Not until 1959 with the acceptance of the L7/M68 as the tank gun of choice did the US Army realize that a shouldered cannon round, that reduced the length of the cartridge, was even possible.

IIRC 3" had small shoulder, as did 90mm, but reason for avoiding it was to have neater and larger ammo storage.

 

[futon]

I vaguely recall some design standard that the gun should not go beyond the front hull practiced by several countries before the war started. But the capabilities competition in the war made penetration more important than that standard. 

 

[Ol Paint]

As I recall, Liberty Ships were originally built with 30-ton booms at No. 2 cargo hold.  Later ships were upgraded to 50-ton booms.  I think hold No.4 started at 15-ton and upgraded to 30-ton later.  So transporting heavier tanks exceeded the capacity of the shipboard handling gear, requiring shore-side cranes to get the tanks on and off the ship.  That slows deployment and makes the logistics more difficult. 

Doug

[Tim the Tank Nut]

regarding the gun tube length versus hull overhang stupidity:

Clearly the people writing those specifications had no practical experience with tank operation.  If you turn the turret the tube is going to overhang the side no mater what.  As far as front overhang goes if you are inside the length of a gun tube then you've maneuvered badly.  Situational awareness between the driver, gunner, and TC is vital.  That is why we have intercoms.

What was anyone going to hit with the gun tube that they weren't going to hit with the fenders a split second later?

If you are going into some crazy ass terrain the elevate and/or traverse.  You aren't successfully targeting anything coming out of a culvert anyway.  If you dig the tube into the dirt then you weren't paying attention to what you were doing.

[Markus Becker]

WAG: Who had practical experience with large armoured formations?

And given the state of armour, the short-ish guns had enough firepower. Until Matilda II, Valentine and Pz's with 20mm add on showed up. 

[DKTanker]

6 hours ago, bojan said:

Since it used same same ammo ballistic loss was probably minimal.

In hindsight they were ofc all wrong, but it is unfair to single out US tank designers for that fault.  

First I want to correct the record.  I repeated a historical myth about the M4 that was only attributable to early M3 mediums.  The M3 medium tank initially was fielded with a cut down M2 75mm gun (31 calibers from 36).  It was soon replaced by the M3 75mm gun which was also fielded with the M4s.  The M3 75mm gun was actually longer than the original M1897 gun from which it was derived (40 calibers from 36).

I'm not singling out US tank designers, that was done by the OP when he titled the thread "US tank design and philosophy".

[DogDodger]

On 1/9/2025 at 4:16 PM, Manic Moran said:

Just on the matter of the M4 with the 90.

 

Thanks, missed that video. Have you ever come across any proposed ammo stowage diagrams for an M4(90) with 70+ rounds? For example, with ammo stowage moved to the floor in late-production tanks, the batteries were moved to the left sponson, so that space would be lost if a similar scheme was used.

[Tim the Tank Nut]

regarding DKTanker's comments:

It seems if I saw somewhere an M3 Lee medium with an enormously long gun tube installed (photo, not real tank).  I guess that was super early production?

[Olof Larsson]

On 1/10/2025 at 2:04 PM, DKTanker said:

Seems that there was a whole raft of actors suffering from the same malady, lack of aforethought. 

Example:  90mm gun construction was the bottleneck is often the argument heard.  What isn't usually noted and queried is that 90mm gun construction was completely halted and apparently the project shelved or even scrapped thus necessitating the entire project being rebirthed from the beginning.

Example:  The original 75mm gun for the M4 was shortened by 8 calibers because the original length inhibited mobility (it stuck out too far).  That's the same argument that was being made about installing first the 76mm and then the 90mm had it been available.

Example:  It would be more than eight months after the M4 was accepted for production that a follow on project was initiated.  People with aforethought would have initiated a new program even before the M4 had been accepted.

Example:  Gun and ammunition design stagnated.  Not until 1959 with the acceptance of the L7/M68 as the tank gun of choice did the US Army realize that a shouldered cannon round, that reduced the length of the cartridge, was even possible.

The US Army started using bottlenecked cases in tank guns in 1935 with the M2 light tank. The 3-inch gun case was also bottlenecked, as was the 57mm, the 76mm the 90mm and so on.

 

The 90mm necked down from 112mm (124% of caliber) to 95mm, with a diameter of 122mm (136% of caliber) just in front of the rim.

The L7 necked down from 129mm (123% of caliber) to 110mm, with a diameter of 137mm (130% of caliber) just in front of the rim.

So percent vise the 90mm used a slightly more bottlenecked case then the L7.

[Manic Moran]

On 1/10/2025 at 8:20 PM, DogDodger said:

Thanks, missed that video. Have you ever come across any proposed ammo stowage diagrams for an M4(90) with 70+ rounds? For example, with ammo stowage moved to the floor in late-production tanks, the batteries were moved to the left sponson, so that space would be lost if a similar scheme was used.

I have not.

[seahawk]

In the end you are looking at it from the wrong perspective. The key was to produce a huge number of good enough tanks. Tanks that ideally would be okay doing infantry support throwing HE and okay fighting enemy tanks. T-34 and M4 were those tanks. Easy to produce and good enough in combat.

[Stuart Galbraith]

Considering we had command of the air, artillery superiority and so many other advantages, we really didnt need tanks that matched the Germans, not least because in the end they had so few of them by the end anyway. And it wasnt as if we werent approaching their qualitative edge by the end anyway.

Not much consolation for anyone in Normandy of course.

[seahawk]

Wrong perspective. Yes meeting a Tiger I in a 75mm Sherman, was bad luck, but if you look at the bigger picture, having more M4s with a decent HE gun, was much more important for the operation, as not every ambush and defence line contained Tigers, but many contained MGs, AT guns and other weapons the M4s could handle.

[DKTanker]

1 hour ago, seahawk said:

Wrong perspective. Yes meeting a Tiger I in a 75mm Sherman, was bad luck, but if you look at the bigger picture, having more M4s with a decent HE gun, was much more important for the operation, as not every ambush and defence line contained Tigers, but many contained MGs, AT guns and other weapons the M4s could handle.

That's a post war perspective which rationalizes the inadequacy of the M4 post 1942 and, incidentally, doesn't account for the pressing need to introduce the M4(76) quite soon after June 1944 and the introduction of the 90mm armed M26 in January of 1945.  If the bigger picture is that lots of HE throwing M4s was always the correct solution then there should have been no need for the M4(76) much less the M26. 

Moreover, fast forward five years, since the NorKs never had more than about 100 T-34s why weren't HE throwing M4s and M24s more than adequate?  After all, the T-34/85 is less a threat than a Panther or Tiger and the SU-76, of which the NorKs had many, would have been no greater a threat than a Pz3 or Pz4.

Edited January 13 by DKTanker

[Stuart Galbraith]

The reason for the failure of 1950 in Korea go a lot deeper than the efficacy of the T34. You can read a report I posted up yesterday stating how miserable the tanks were after inspection.

[seahawk]

They were adequate. And many nations supporting the UN did use them. But the numbers of tanks needed was small compared to WW2 needs, so nations who could afford to sent their best tanks, did sent their best tanks. But if you would have the option to have 50 M46 or 150M4s - the answer would be clear.

My point is a lot of decent tanks is better than a smaller number of good tanks.

To put numbers into perspective. We are talking about 1350 Tigers, ~ 500 Tiger 2, and 5.000 Panther. Compared to 49.000+ M4s. Add 57.000 T-34s - to give you an indication of scale.

So roughly 7.000 German Big Cats vs. 100.000 standard tanks with the enemy. Even if you add the 8.000 Pz IV to the German side. It should be obvious that the chance of an allied tank meeting a German tank was rather small.

 

Add that the 75mm could penetrate the sides of German tanks, while the 76mm needed the HVAP-T ammo to be a clear improvement for shots against the frontal armour. But if you give the 75mm the HVAP T45 ammo, it is also adequate.

Edited January 13 by seahawk

[Manic Moran]

There was always an intent that US tanks should be able to meet enemy tanks on at least equal terms. That 75mm tanks could and did take out Tigers and Panthers was more a happy happenstance than the intended endstate. It's why the initial intent for the 76mm tank was 100% fielding, with no 75mm tanks at all. That said, after Fifth Army put in the request for 90mm tank destroyers, they then reversed it with a "Actually, belay that. Only send us the 90mm guns after we're sure that the vehicles work. We would prefer known working equipment than the latest which nobody is comfortable with yet. We'll take 3-inchers instead for now"

Of course, later the intent for the 76mm gun was not 100% replacement, but to work in company with the 75mm. I have not seen the official documentation explaining the rationale, but there are two which come to mind, one more likely than the other.

1) The desire to keep the 75mm around as a more effective HE chucker.

2) The fact that in between the original 100% intent and the actual switch to 76mm tank production, there were a couple of false starts and about a year of massive production of 75mm tanks. Bear in mind the US turned down the tank production taps after 1943, they felt they had built more or less enough to prosecute the war. Total replacement of the 75mm with a 76mm would require replacing all those thousands of tanks built during the massive production year of 1943, production in far excess of what was needed to win the war. The Government had other things to do with the money, steel, and manpower, including switching to an entirely new tank in the near future.

My money's on #2.

[Tim the Tank Nut]

I took the time to watch the videos.  It made enough impact that I started a thread in the History forum.

Regarding the 75 vs 76mm forever debate the real answer was always better ammo for both.

[old_goat]

Unfortunately, all of this is just one side of the coin. Without eastern front experience, the picture is not clear. And the 75mm Shermans didnt really shine there. For example, during the german relief attempts of Korsun pocket, the soviets used lots of Shermans. They werent effective at all, in fact, T-34/76s were more suitable because they had higher mobility in the ground  conditions found there. Tank vs tank, M4A2s werent worthy opponents for Tigers and Panthers. (Számvéber Norbert : Ragadozók - A "Bäke" nehézpáncélos-ezred története, 1944. január-február Sorry, this is only in hungarian. But this is an extremely well researched book, using lots of original soviet sources)  

Later, when the 76mm tanks appeared, things changed dramatically. They were not only better than T-34/76s, but also superior to T-34/85. 76mm gun was definitely needed. Everybody was talking about Tigers and Panthers. But not about Panzer IVs and Stugs. 75mm was barely adequate against these. 76mm on the other hand, extremely effective. 

[Markus Becker]

8 hours ago, seahawk said:

Wrong perspective. Yes meeting a Tiger I in a 75mm Sherman, was bad luck, but if you look at the bigger picture, having more M4s with a decent HE gun, was much more important for the operation, as not every ambush and defence line contained Tigers, but many contained MGs, AT guns and other weapons the M4s could handle.

Wrong perspective indeed. What's wrong meeting a Tiger I in a 75mm Sherman, if you have 75mm APCR ammo? 

Even that allegedly inferior gun could have done the job with ease. 

[RichTO90]

I see a lot of people haven't bothered to read my book and haven't bothered to follow Manic's videos. 🤪