"sherman mixing" Topic

How probable would it have been historicaly to have platoons of m4-75 and m4-76 mixed together? Say 3 of the 75s with 2 76s along with. Ive been told this would be rare as the platoons were either all of one or all the other. What about replacements? Could m4-76s be sent to replace lost m4-75s?
Thanx

Just to check, are we just talking US? In French service one 76 per platoon was common – they didn't get many, and those were indeed replacements, so they used them in similar fashion to the Brits with the Firefly.

Very likely – proportion of 76mm in platoons steadily increased throughout the NW Europe campaign. Some armoured divisions arriving later in the campaign were fully equipped with 76mm on arrival but even these got some 75mm models as replacements for losses.

Depends, some were mixed some weren't, it was pretty much on a Division by Division or even by Battalion basis.

jdg

What Bill said. Commanders kept a fair proportion of the 75mm tanks because contrary to what Hollywood and the panzer fans would have you believe, it was pretty rare to encounter a German tank at all – and if you did it was more likely to be a Stug or Hetzer.

The 75mm HE shell was far better suited to taking out the Sherman's most common opponents – dug in infantry, bunkers and gun emplacements, which was the job the Sherman was designed for.

Early in Normandy not very common, and even during Cobra I dont think it would have happened due to lack of training on the new gun system. Patton refused them during his start as 3rd Army CO for that reason. Later on, probably you could get away with it, though tankers in an infantry support role wouldn't have the 76 due to no HE.

Bit confused by your statement of no HE with the 76 recon35. There was indeed a standard HE round issued for the 76 and carried by those tanks so armed. The original round was far inferior to that issued to the 75mm gun tanks and even the redesigned HE round was not quite up to the 75 round but there was indeed plenty of 76 HE rounds.

For comparison the original 76mm HE round weighed in at 12.7 lbs and had .86 lbs of explosive. The standard 75mm HE round weighed in at 14.6 lbs and had 1.47 lbs of explosive.

IIRC trials by the War Office showed the 76mm HE was approximately 30% less lethal than 75mm HE, a problem with all high velocity 75/76mm rounds (be they US or fired from a 75L70 or a 17pdr).

It still made a pretty big bang though.

Also, of interest, according to Zaloga and unfortunately NOT broken out by type, US tankers as a whole in Europe fired about 70 percent HE, 20 percent AP and 10 percent smoke/illuminating rounds. Would be more helpful if broken out by types as, for example, the 105mm armed Shermans would fire HE, smoke and illuminating rounds exclusively which may tend to skew stats.

Well the usual theory is that the higher velocity requires a stronger container and hence less HE filler. However, comparison with the rather effective HE rounds available to various high velocity German guns suggests the designers maybe weren't trying all that hard….

"was the difference because of the velocity or because of the amount of explosive"

It was in one of John Salts compendious War Office compilations WO 291/741

This is what it actually says:

WO 291/741 Comparison of the performance of 75mm and 76mm tank gun ammunition.

The 75mm M48 is longer and heavier than the 76mm M42A1 and has greater capacity. 76mm M42A1 is assumed identical to the 3-inch M42A1. All three use the M48 fuze.

Vulnerable areas against men in the open, in square feet, are given as:

3" or 76mm M42A1 2200 sq ft
75mm M48 2900 sq ft

"Thickness of homogenous armour plate penetrated at 30°angle of attack by APCBC/HE shell."
Ranges in yards.

Range 75mm 76mm
Point blank 79.5 108.2
200 75.3 104.2
400 72 100.2
600 68.5 96.7
800 65.5 93
1000 63 89.7
1200 60.3 86.3
1400 57.8 83.1
1600 55 80
1800 52.6 77
2000 50 74

The report concludes that, whereas lack of HE performance can be compensated for by using more of the less effective shell, lack of penetrating power cannot be made up for in this way.

So the 76 isn't hugely worse at HE than the 75 (2200 vs 2900) and the solution is just to fire more shells.

I am not for a moment suggesting that the relationships are linear but we could take as a very rough number from this that the 76mm HE is up to 25% less effective. Yes, when firing at targets in the open the difference can be made up by spraying more shells around, in effect delivering the same quantity of HE onto the target area. What isn't clear is the difference in HE performance against hard point targets like solid cover or buildings.

BTW, Bird & Livingston's "Armor and Gunnery" work contains a summary of projectile and HE filler weights for various tank and AT gun HE projectiles. Most of this info (apart from the Russian data) is sourced from WO 291/955 which I think can be found among J. Salt's material. The same info is also presented in the following link along with some other interesting and relevant tidbits…

link

Not to veer off course but a very good site for guns vs armor can be found here:
freeweb.hu/gva/index.html