US tank design and philosophy

[EchoFiveMike]

One thing I have noticed is the disappointing performance of the 3" gun.  Given it's larger chamber volume, it should be firing the 15.5lb M62 shell or M79 shot at 2800-2900fps if the propellant were optimized.  I assume that it's USN heritage lead to a common propellant and longer barrel life loading being prioritized over performance.  

Also a reduced velocity cast iron HE frag would have made a lot of sense too.  Since this was the most common ammunition fired, the reducing in barrel wear would mitigate the increased barrel wear of high performance AP ammunition.   S/F....Ken M  

Edited January 15 by EchoFiveMike

[Markus Becker]

45 minutes ago, EchoFiveMike said:

One thing I have noticed is the disappointing performance of the 3" gun.  Given it's larger chamber volume, it should be firing the 15.5lb M62 shell or M79 shot at 2800-2900fps if the propellant were optimized.  I assume that it's USN heritage lead to a common propellant and longer barrel life loading being prioritized over performance.  

From Wikipedia: 

"The M79 AP shot could penetrate 92 mm of homogeneous armor angled at 30 degrees from the vertical at 1,000 yards. The M62 APCBC/HE-T shell was capable of penetrating 88 mm of homogeneous armor under the same conditions The T4 (later M93) HVAP shot was rare and was used in small numbers beginning in September 1944. It could penetrate 135 mm of homogeneous armor at 30 degrees and 1,000 yards."

 

You are more or less getting the best penetration of the 75mm at 500 yards at 1,000 yards. Ok, I get it that they could have done even better but that doesn’t look disappointing to me. 

[DogDodger]

15 hours ago, Interlinked said:

I stand corrected. Poor M47 doesn't get the recognition it deserves once again.

Definitely much-maligned. At least Telly Savalas respected it.

13 hours ago, futon said:

Wiki has T-34-85 1943 model starting production in Janu... ohhhh I checked again, it looks like its January 1944 to March 1944. I took it as January 1943 to March 1944. Oopsie. 

Understandable with the model naming  used.

[RichTO90]

3 hours ago, EchoFiveMike said:

One thing I have noticed is the disappointing performance of the 3" gun.  Given it's larger chamber volume, it should be firing the 15.5lb M62 shell or M79 shot at 2800-2900fps if the propellant were optimized.  I assume that it's USN heritage lead to a common propellant and longer barrel life loading being prioritized over performance. 

The Army 3" was a different beast than the Navy 3". The Army 3" was originally developed as a Coast Artillery gun, then was adapted as an AA gun, and then was adapted again as a Tank gun, before it was again redesigned as the 76mm gun.

Quote

Also a reduced velocity cast iron HE frag would have made a lot of sense too.  Since this was the most common ammunition fired, the reducing in barrel wear would mitigate the increased barrel wear of high performance AP ammunition.   S/F....Ken M  

Yep.

[shep854]

5 hours ago, DogDodger said:

Definitely much-maligned. At least Telly Savalas respected it.

Well, it did look mean enough for the King Tiger role.

[R011]

2 hours ago, shep854 said:

Well, it did look mean enough for the King Tiger role.

Especially compared to the M24 "Shermans".

[EchoFiveMike]

8 hours ago, RichTO90 said:

The Army 3" was a different beast than the Navy 3". The Army 3" was originally developed as a Coast Artillery gun, then was adapted as an AA gun, and then was adapted again as a Tank gun, before it was again redesigned as the 76mm gun.

Yep.

With the caveat that it's just internet research, for the point of the argument, the chamber volumes and case dimensions are the same.  Regardless, the ~215 cu inch chamber volume of the 3" should have provided significantly superior performance than what it did.  The fact that the performance was duplicated by the ~75 cu inch smaller 76mm is evidence of that.  A 2900fps 3" AP with the USN non-suck projectile would have resolved the issue other than the Panther glacis.  S/F....Ken M 

[LeeWalls]

10 hours ago, RichTO90 said:

The Army 3" was a different beast than the Navy 3". The Army 3" was originally developed as a Coast Artillery gun, then was adapted as an AA gun, and then was adapted again as a Tank gun, before it was again redesigned as the 76mm gun.

Yep.

"The bastard son of a thousand maniacs."

Nightmare on Elm Street

[bojan]

17 hours ago, Markus Becker said:

...superior accuracy of the 76mm...

IIRC dispersion wise 76mm was not much better than 75mm. Real champion was 90mm (fired from M36), which had 10cm/16cm vertical/horizontal dispersion @ 1000m, which is ~0.1 x 0.16 MOA.

[futon]

IIRC, the 76mm had better accuracy than the 17 pounder so that may be the basis for good accuracy reputation. That's if I'm not wrong again though.

[bojan]

Dispersions of practically every WW2 tank gun of 75mm+ caliber was perfectly adequate for the most common use, shooting HE at less than 1000m.

Even if one or other was more accurate differences were not that large. Soviet 122 D-25 is often was quoted as "inaccurate", but it's dispersion @ 1000m was IIRC (going from memory) ~21x28cm. "Very accurate" 88/71 dispersion was (again, going from the memory) ~18x25cm. So what was a practical difference at any WW2 combat range up the 2km (especially long range for WW2 combat even on the Eastern front in 1944-45)?

"Accuracy" was often catch-all term for multiple factors, eg how flat shooting weapon was (which reduced ranging errors), how observable was fall of shot, how much gun and vehicle shook after firing etc. So all stories about "accurate this, inaccurate that" have to be taken with a big grain of salt.

[Manic Moran]

3 hours ago, bojan said:

IIRC dispersion wise 76mm was not much better than 75mm. Real champion was 90mm (fired from M36), which had 10cm/16cm vertical/horizontal dispersion @ 1000m, which is ~0.1 x 0.16 MOA.

As far as the US was concerned, with data available in 1946, the 76mm was considered more accurate than the 90mm, but the gap was much smaller than for either to 17pr.

But, yes, at typical ranges, the difference is relatively academic.

[RichTO90]

7 hours ago, EchoFiveMike said:

With the caveat that it's just internet research, for the point of the argument, the chamber volumes and case dimensions are the same.  Regardless, the ~215 cu inch chamber volume of the 3" should have provided significantly superior performance than what it did.  The fact that the performance was duplicated by the ~75 cu inch smaller 76mm is evidence of that.  A 2900fps 3" AP with the USN non-suck projectile would have resolved the issue other than the Panther glacis.  S/F....Ken M 

That was because they originally were different designs for the same purpose; to shoot at ships. 😂

Regardless, the issue of Mv is a red herring, since the real problem was that increasing the Mv in the 3"/76mm would have reduced its effectiveness against most of the German armor. It was the projectile and fuze design that was poor, not the gun design. While somewhat over engineered - it was a late 18th century/early 20th century design after all - that only made the gun somewhat heavier than the German Kwk/PaK 40, which really only affected the towed 3" (and was no real advantage in the PaK40).

[RichTO90]

3 hours ago, bojan said:

IIRC dispersion wise 76mm was not much better than 75mm. Real champion was 90mm (fired from M36), which had 10cm/16cm vertical/horizontal dispersion @ 1000m, which is ~0.1 x 0.16 MOA.

You may be correct; I was more thinking of the 76mm firing HVAP, compared to the 76mm APC and the 75mm APC.

[Murph]

10 hours ago, EchoFiveMike said:

With the caveat that it's just internet research, for the point of the argument, the chamber volumes and case dimensions are the same.  Regardless, the ~215 cu inch chamber volume of the 3" should have provided significantly superior performance than what it did.  The fact that the performance was duplicated by the ~75 cu inch smaller 76mm is evidence of that.  A 2900fps 3" AP with the USN non-suck projectile would have resolved the issue other than the Panther glacis.  S/F....Ken M 

Could it have been different powder used in the tank cannon?

[Murph]

On 1/13/2025 at 10:19 PM, RichTO90 said:

No, I doesn't because that is a total misreading of what that says. I do talk about why that particular M4(105) on the assembly line was pulled aside and had a T26E3 turret assembly dropped onto it for that photo op though. The problem is that they were already putting 90mm guns on M4 chassis, but they weren't tanks, they were tank destroyers. Putting T26E3 turrets on M4 chassis was a non-starter because they needed the T26E3 turrets to put on T26E3 chassis. The turret was not an excess item.

The Armored Force saw the 75mm as more than adequate...well, until Devers took over from Chaffee who was dying. Devers was an artilleryman and saw the advantage of more powerful guns. OTOH, the Armored Force wanted adequate ammunition storage, so their ideal was well described to Ordnance - it was basically an American version of the 7.5cm KwK 42. So Ordnance said, we have a better idea, like it or lump it, we'll design a tank around the 90mm. Wait a second sez Armor, can you give us 70+ rounds of stowage. Sure sez Ordnance, and deliveries the T26E3 with 59 rounds of stowage. Wait sez Armor...you see where this goes.

Meanwhile, the 76mm M1 Gun was a perfectly find gun, with a terrible APC projectile and worse fuzing. Wonderfully accuracy, but against heavy armor the projectile tended to deform or the fuze actuated early or both. Oh, BTW, the Navy designed 3" APC projectiles were superior in design to the Army, but the Army did not know that until they were tested side by side...in 1946. Oh, Ordnance also knew the German designed projectiles were far superior, as early as April 1943, and made zero effort to copy the design specifications.

Tell me how all that is McNair's or AGF's fault.

I cud go on an on but I would prefer you read the book and then ask questions.

 

 

Was there a turret ring size difference between the 105 version, and the "regular" Sherman which would account for the difference?

[bojan]

AFAIK all Shermans (irrespective of turret or armament), M-36, M-18, M26 had same turret ring diameter.

4 hours ago, Manic Moran said:

As far as the US was concerned, with data available in 1946, the 76mm was considered more accurate than the 90mm, but the gap was much smaller than for either to 17pr.

Interesting, I will try to find my data* for 76mm, , I vaguely remember that 76mm had slightly more dispersion with AP than 90mm.

*I highly suspect it is US in origin, just translated locally, since some data is given in very "awkward" measurements, like "158.7mm" for 90mm vertical dispersion  , which is 6&1/4" rounded to one decimal point (instead of 158.75) and "104.8mm" horizontal dispersion, which is again 4&1/8" rounded to a single decimal point (104.775mm).

[RichTO90]

3 hours ago, Murph said:

Was there a turret ring size difference between the 105 version, and the "regular" Sherman which would account for the difference?

No. What difference?

[Murph]

Fitting a larger turret to accommodate a bigger gun.

[RichTO90]

4 hours ago, Murph said:

Could it have been different powder used in the tank cannon?

I should look more closely and responded more fully. The chamber of the 76mm Gun M1 was 142.6 cubic inches. That of the 3" Gun M7 was 205.58. The maximum chamber pressure of the M1 was 43,000 p.s.i. The maximum chamber pressure in the M7? 38,000 p.s.i. The propellant charge in the M1 was 3.62 pounds of FNH powder. In the M7 it was 4.62 ponds of NH powder.

[RichTO90]

7 minutes ago, Murph said:

Fitting a larger turret to accommodate a bigger gun.

It was not a bigger gun. The 105mm M4 was a howitzer.

[Ssnake]

...unless we're talking about Israeli Super Shermans...

[Stuart Galbraith]

I think the turret they mounted the 105mm into was just a standard 75mm Sherman gun turret wasnt it? The one I modelled appeared to be just that, but with the addition of a loaders hatch to the left of the commanders, which may have been on late production 75mm versions anyway.

It was an interesting thing to discover that the Shermans in Kellys Heros had likely been 105mm armed Shermans (or components thereoff) before being kitbashed into 76mm's for supply to allies. The idea seemed to be to hold onto all the HVSS supplied hulls, and supply all the other ones with the earlier suspensions abroad.

The Super Sherman I think was based on the T23 turret, although the Israelis kitbashed their stuff so many times there may be exceptions. There certainly was a variant with the gun extended out the front of the turret, Ive an inkling those might be the earlier turrets.

Just checked, it was M51s in the T23 turrets, the M50 seemingly used the earlier 75mm gun turrets.

Edited January 17 by Stuart Galbraith

[Murph]

16 hours ago, RichTO90 said:

It was not a bigger gun. The 105mm M4 was a howitzer.

NO, what I am asking is if the turret which held the 105mm was larger and required a larger turret ring to make it fit on the tank compared to the 75mm turret?

[RichTO90]

3 hours ago, Murph said:

NO, what I am asking is if the turret which held the 105mm was larger and required a larger turret ring to make it fit on the tank compared to the 75mm turret?

Oh, sorry, no it did not. The turret was the same, the gun/howitzer and its mount were different. The 105mm used the M52 (T70) Combination Gun Mount. The 75mm used the M34 and M34A1 Combination Gun Mount. The 76mm used the M62 Combination Gun Mount. The original 75mm turret D58708 and its development variant D78461 were used for the 75mm Mount (aside for a few pilot 76mm and 105mm) and the D78461 was also used for the 105mm. The later "T23" D82081 turret was used the 76mm.

Interestingly enough, one critical point seems to have been the recoil stroke, which were all pretty much the same for the 75mm, 76mm, 90mm, and 105mm (howitzer) at right around 12 7/8 inches.

Edited January 17 by RichTO90