USA: Early M4 hulls with L40 gun? - Page 2

Pibwl · #1 October 29th, 2016, 02:08 PM

Quote:

Originally Posted by Griefbringer

Quote:

Originally Posted by Mobhack

(I can see why we Brits renamed US things with real names in WW2, not some M-number and a jumble of letters and digits..

Which M3, did sir mean - the light tank M3, half track M3, the medium tank M3, the M3 SMG, the Tractor Crane (2 ton) M3. Much easier to use proper names for things!

)

Don't forget the M3 howitzer (not to be confused with M3 gun).

And how about M3 Scout car?

jp10 · #2 October 30th, 2016, 01:03 AM

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?

Copernicus · #3 October 30th, 2016, 01:22 PM

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?

Cross · #4 October 30th, 2016, 06:59 PM

Quote:

Originally Posted by Copernicus

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

jp10 · #5 October 30th, 2016, 09:03 PM

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.

Cross · #6 October 30th, 2016, 10:26 PM

Quote:

Originally Posted by jp10

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

Cross · #7 October 30th, 2016, 10:34 PM

Quote:

Originally Posted by jp10

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

Cross · #8 October 31st, 2016, 07:02 PM

Quote:

Originally Posted by Cross

Quote:

Originally Posted by jp10

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

Copernicus · #9 October 31st, 2016, 12:55 PM

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).

jp10 · #10 October 31st, 2016, 08:43 PM

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.