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  #11  
Old October 30th, 2016, 02:03 AM

jp10 jp10 is offline
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Default Re: USA: Early M4 hulls with L40 gun?

the M4A3E2 Assault Tank had Grousers fitted to the tracks. Don't forget about Grousers. Other than the US, the Free French units received one M4A3E2.
I am psychologically crushed beyond relief that Grousers and the lone Free French tank are being shunned by the war gaming community.
Where's the love?
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  #12  
Old October 30th, 2016, 02:19 PM

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Default Re: USA: Early M4 hulls with L40 gun?

Quote:
Originally Posted by Cross View Post

As for hulls.


I think there were 6 hull types:
  • Early Cast dry tiny hatches
  • Late Cast wet large hatches
  • Early Welded dry small hatches
  • Late Welded wet large hatches
  • Composite welded
  • HVSS Wider with wider tracks
There were some welded (M4A2) and cast (M4A1) hulls with dry stowage and large hatches (in the M4A2's), if these sources are accurate:

Quote:
"Starting in late 1943, the 56° glacis on the M4A2 was replaced by a single-piece plate inclined at 47° from vertical. The 56° glacis featured protruding drivers' hoods with direct vision slots on early tanks and periscopes on later vehicles, and the glacis plate was composed of several pieces welded together, which complicated production. The 47° plate was a single piece and eliminated the drivers' hoods. Larger drivers' hatches were also introduced with the 47° plate. 75mm gun M4A2s were produced with dry stowage and the 47° glacis until replaced on the factory line in May 1944 by wet stowage 76mm gun tanks."
Quote:
"In late 1943, M4A1 hulls were changed to incorporate larger drivers' hatches and a thicker 2.5" (6.4cm) glacis inclined at 47° instead of 56°. About 100 M4A1s were built with the 47° glacis and dry stowage, and all of these were armed with the 75mm gun M3. Unlike earlier dry stowage tanks, the castings themselves on these vehicles were thickened over the vulnerable areas."
http://afvdb.50megs.com/usa/m4sherman.html#M4A2

---

Quote:
"Our Archival research has not as yet uncovered any documentation that states exactly when the large hatch, welded hull Sherman entered production, but it is thought that the M4A2(75) shown above may have been one of the first. This tank was evaluated at General Motors Proving Ground and is stated to have been Serial Number 27283 / USA 3035813 indicating November 1943 acceptance. The large hatch M4A2(75) was slated for termination, and did NOT incorporate one of the features of the "ultimate Sherman" - Wet Stowage. Consequently appliqué armor was factory installed on the sides of the hull to protect the ammo bins which remained mounted on the sponsons as on the original Sherman design."
http://the.shadock.free.fr/sherman_m...gehatches.html

Granted, that's not very many. And the M4A2's were mostly (exclusively?) USMC. And the 105mm armed versions had a stowage that was not wet, but offered other modifications that achieved the same effect, if I'm understanding it correctly.

---

All of this looks to be pretty well represented in the game, by the way. Large hatches improved crew survivability by allowing for better escapes, I assume. And wet stowage greatly decreased ammunition fires (although it had little to do with wetness). From what I can tell:

Survivability 2 = Dry stowage small hatch.
Survivability 3 = Dry stowage large hatch.
Survivability 4 = Wet stowage large hatch.

Additionally, the frontal armor values:

Cast small hatch: 51mm @ 55 deg.
Cast large hatch: 64mm @ 47 deg.

Welded small hatch: 51mm @ 56 deg.
Welded large hatch: 64mm @ 47 deg.

I'm led to believe that the cast hulls offered less protection than the welded ones for the same armor values, though.

(All HVSS hulls had the large hatches, I think, except for a few post-war modified tanks. I'm not sure where the composites fit into this.)
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  #13  
Old October 30th, 2016, 02:22 PM

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Default Re: USA: Early M4 hulls with L40 gun?

Oh, but back to the actual question of the thread:

Cross, do you think you can confirm that there was only one actual version of the 75mm M3 gun, and that the alleged two lengths were just rounding or different measuring?
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  #14  
Old October 30th, 2016, 07:59 PM
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Default Re: USA: Early M4 hulls with L40 gun?

Quote:
Originally Posted by Copernicus View Post
Oh, but back to the actual question of the thread:

Cross, do you think you can confirm that there was only one actual version of the 75mm M3 gun, and that the alleged two lengths were just rounding or different measuring?


I can tell you that a primary US document lists the gun length as 118.36 inches, which is 3007mm or L40.

I don't know how they measured, but there's no muzzle brake to muddy the waters, and if they included the breech, as they do on the continent, then the breech would have to be about 20cm to explain a L37 or L37.5 length.





cross
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  #15  
Old October 30th, 2016, 10:03 PM

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Default Re: USA: Early M4 hulls with L40 gun?

According to FM 23-95 75-MM TANK GUN M2 (MOUNTED IN MEDIUM TANK M3)
May 4, 1942, the gun was measured "Length (muzzle to rear face of breech ring)". I would imagine it would be the same for the 75-MM Tank gun mounted in Medium Tank M4.
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  #16  
Old October 30th, 2016, 11:26 PM
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Default Re: USA: Early M4 hulls with L40 gun?

Quote:
Originally Posted by jp10 View Post
According to FM 23-95 75-MM TANK GUN M2 (MOUNTED IN MEDIUM TANK M3)
May 4, 1942, the gun was measured "Length (muzzle to rear face of breech ring)". I would imagine it would be the same for the 75-MM Tank gun mounted in Medium Tank M4.
It's my understanding that the rear of the breech is farthest from the loader and where the bore begins. This would appear to confirm that the L40 does refer to a bore length of 3007mm.

Cross
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  #17  
Old October 30th, 2016, 11:34 PM
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Default Re: USA: Early M4 hulls with L40 gun?

Quote:
Originally Posted by jp10 View Post
According to FM 23-95 75-MM TANK GUN M2 (MOUNTED IN MEDIUM TANK M3)
May 4, 1942, the gun was measured "Length (muzzle to rear face of breech ring)". I would imagine it would be the same for the 75-MM Tank gun mounted in Medium Tank M4.
It's my understanding that the rear of the breech is farthest from the loader and where the bore begins. This would appear to confirm that the L40 does refer to a bore length of 3007mm.

Cross
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  #18  
Old October 31st, 2016, 01:55 PM

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Default Re: USA: Early M4 hulls with L40 gun?

So it sounds like, unless anyone has any information to the contrary, there did not exist two distinct 75mm guns for the Medium Tank M4. 75mm/L37 and 75mm/L40 were simply two different ways of measuring the same gun.

In that case, Mobhack, the fix would be to simply replace all L37 guns (#45) with the L40 (#47).
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  #19  
Old October 31st, 2016, 08:02 PM
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Default Re: USA: Early M4 hulls with L40 gun?

Quote:
Originally Posted by Cross View Post
Quote:
Originally Posted by jp10 View Post
According to FM 23-95 75-MM TANK GUN M2 (MOUNTED IN MEDIUM TANK M3)
May 4, 1942, the gun was measured "Length (muzzle to rear face of breech ring)". I would imagine it would be the same for the 75-MM Tank gun mounted in Medium Tank M4.
It's my understanding that the rear of the breech is farthest from the loader and where the bore begins. This would appear to confirm that the L40 does refer to a bore length of 3007mm.

Cross

I've contradicted myself...
If the continental armies also measured from the "rear face of the breech" then the USSR and Germany also used a bore length to determine the L** calibers, and my original source is wrong.

Don't you love rivet counting


Cross
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  #20  
Old October 31st, 2016, 09:43 PM

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Default Re: USA: Early M4 hulls with L40 gun?

From reading the manual, and looking at the diagrams it seems that only the threaded front part of the breech where the barrel screws into would be in the measurement.
3. DESCRIPTION OP GROUPS.—a. Gun group.—(1) Tube.— The tube (fig. 1) is formed of one piece of alloy steel. The rear end of the bore is suitably tapered to form the chamber, and from chamber to muzzle the bore is rifled with a uni form right hand twist of one turn per 25.59 calibers. The exterior of the breech end is threaded to screw into the 75-MM TANK GUN M2 breech ring, and the shoulder immediately forward of the threads contains a keyseat for the breech ring key. Forward from the breech ring the exterior is cylindrical and smoothly finished for bearing in the mount for approximately half the length of the tube. The breech face of the tube is re cessed on each side of the bore to form extractor camming surfaces (fig 3).

https://www.ibiblio.org/hyperwar/USA...Fs/FM23-95.pdf

if you want to see the diagrams.
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