Sherman 76 question

[Lt Belenko]

I'm reading Hiltler Last Gamble - Dupuy. In the appendices, he states that the Sherman 76 really was a 75mm but just a longer, high velocity gun.

I had never heard this before. True?

[dieseltaylor]

http://en.wikipedia.org/wiki/76_mm_gun_M1

answers your query

Essentially you need also a different shell to take advantage of the different gun length and all that is a function of making an ATG specific weapon.

[Pak40]

I have the same book and remember reading that a long time ago. It's not true, the the 76mm gun was 76.2mm and the 75mm gun was a true 75mm. IIRC, The 3" guns (used for M10s) were also 76.2mm but couldn't use the same ammo as the 76mm guns, so to avoid confusion they called them 3" guns.

[Lt Belenko]

I have the same book and remember reading that a long time ago. It's not true, the the 76mm gun was 76.2mm and the 75mm gun was a true 75mm. IIRC, The 3" guns (used for M10s) were also 76.2mm but couldn't use the same ammo as the 76mm guns, so to avoid confusion they called them 3" guns.

Yeah, confused the crap out of me. Everything else I've read says was a 76.

[Michael Emrys]

IIRC, The 3" guns (used for M10s) were also 76.2mm but couldn't use the same ammo as the 76mm guns, so to avoid confusion they called them 3" guns.

We might need to do a check on that. I've read in several places that Sherman 76 mm guys often worked a deal with M10 guys in order to get HVAP munitions in exchange for HE, which the M10 guys were using more of than had been anticipated. The Sherman guys often couldn't get HVAP at all through the usual supply channels, or only a tiny trickle.

Michael

[JonS]

ISTR that a version of the 17-pr with a shorter barrel was developed to fit into ... the Challenger? It also had some changes to the breech, I think, and the combination mean that it used a reduced charge, and a smaller cart case.

In order to simplify logistics they arbitrarily changed the designation of the ammo. Full length 17-pr (towed, as well as the ones mounted on Shermans and in M10s) were "17-pr", while the shorted version was "77-mm".

Ah, here we go: http://en.wikipedia.org/wiki/17-pounder#77_mm_HV

As the breech length of the 17-pounder was too long to fit in many tanks, a new version was designed with a shorter breech, firing the same projectile as the 17-pounder from a 3-inch 20 cwt AA gun cartridge through a shortened 17-pounder barrel. This new gun's ammunition was not interchangeable with the 17-pounder, so to prevent confusion over ammunition supplies, it was renamed the "77 mm HV"—the 'HV' standing for High Velocity—although it was the same 76.2 mm calibre as the 17-pounder. This gun was used in the Comet tank.

It wasn't actually 77mm, they just called it that to prevent confusion. And they didn't use 76mm because the American gun was already using that.

[Kanonier Reichmann]

@JonS

The AFV you're thinking of that mounted the modified 17 pounder gun was the Comet tank. The Challenger had the full size version of the 17 pounder but a very tall open topped turret in order to accomodate it.

Personally, the Comet is one of my favourite tanks of WWII in terms of looks and function, seeing as it had quite a low profile for an AFV that was very fast yet still powerfully armed with it's very effective 'de-tuned' 17 pounder.

Regards

KR

[Pak40]

We might need to do a check on that. I've read in several places that Sherman 76 mm guys often worked a deal with M10 guys in order to get HVAP munitions in exchange for HE, which the M10 guys were using more of than had been anticipated. The Sherman guys often couldn't get HVAP at all through the usual supply channels, or only a tiny trickle.

Michael

Yea, as I recall it was only some of the ammo that was incompatible. I'll have to re-check my source: American Arsenal

[MikeyD]

To confuse matters even more, I read reports of M10 TDs in Europe obtaining Navy 3 inch star shells which they used in a direct fire role to great effect, rather like WP. I don't believe the guns were compatible due to different shaped shell casings. This brings up the prospect of a cottage industry developing of rounds being swapped out onto different shell casings. Didn't something similar happen in Tunisia, swapping out American plain AP for 'liberated' German capped 75mm AP rounds?

[Michael Emrys]

Didn't something similar happen in Tunisia, swapping out American plain AP for 'liberated' German capped 75mm AP rounds?

Never heard about that in Tunisia, but earlier in the war the Brits had a shop in the Delta doing something like that, but I do not recall the details.

Michael

[JonS]

Niall Barr, Pendulum of War, p.61-62

However, the very speed of the M3 programme led to real difficulties for the Eighth Army in attempting to use, modify and repair American tanks thousands of miles from the factories producing them. Even before the Grant went into action [in May 1942], British ordnance experts had discovered numerous flaws in it. Perhaps the most important was that the American M72 armour-piercing shell fired by the Grant’s 75mm gun was of little use against German armour. The archaic steel shot simply shattered against face-hardened plate armour. British ordnance experts hit upon an ingenious solution to give the Grant’s main gun much better performance. The British had captured large stocks of German 75mm armour-piercing rounds, and these were used to ‘cap’ the American explosive charge. It was found that these composite rounds fitted perfectly, and, thanks to the hardened German steel projectile, gave very good penetration results against German armour plate.

[Pak40]

Michael,

Found this on page 287 of the American Arsenal:

Shell, High Explosive, 3 Inch, M42A1

Projectile, APC, 3 Inch M62A1

Shell, Smoke, 3 Inch M88

Shot, AP, 3 Inch, M79

The three projectiles above are classified as standard for use in the guns 76mm, M1 M1A1, and M1A2. Three-inch shells may be used since the gun is actually 76.2mm, or 3 inches in caliber. The principal difference between the 3 inch and the 76mm complete rounds is in the capacity of the cartridge case. Due to this, the rounds are not interchangeable between the 3 inch and 76mm guns.

To clarify:

The M7 3 inch gun on the M10 Tank Destroyer uses complete rounds that have the Mk. II M2 Cartridge case (a diameter of 4.27 inches at the base of the cartridge).

The M1, M1A1, and M1A2 76mm gun in the Shermans use complete rounds that have the M26 Cartridge Case (a diameter of 3.566 inches at the base of the cartridge)

BOTH the 3" and the 76mm guns use a 3" shell or projectile. In fact, they both use the M42A1 H.E. shell.

Therefore, what I think was happening is that the M10 units were bargaining for the 76mm HE rounds, but they had to separate the M42A1 shell from the M26 Cartridge Case and put it onto a Mk. II M2 Cartridge case.

[Michael Emrys]

Interesting, Pak40, thanks for the research. That leaves me wondering how the Sherman crews were able to use the HVAP rounds they allegedly got from the M10 crews. Of course, it is possible my source (and I don't remember even what it was) made the whole thing up or was just passing along a rumor. Frustrating.

Michael

[Pak40]

I suspect all of the projectiles from the 3" rounds and 76mm rounds were interchangeable, so long as they used the correct cartridge case. I don't recall seeing a HVAP round listed for the 3" gun, but I can look that up later.

[michael Dwyer]

To confuse matters even more, I read reports of M10 TDs in Europe obtaining Navy 3 inch star shells which they used in a direct fire role to great effect, rather like WP. I don't believe the guns were compatible due to different shaped shell casings. This brings up the prospect of a cottage industry developing of rounds being swapped out onto different shell casings. Didn't something similar happen in Tunisia, swapping out American plain AP for 'liberated' German capped 75mm AP rounds?

IIRC the M-10's gun was adapted from the 3" Naval anti aircraft gun. So using a naval AA shell would have been no problem.

On the other point of swapping HVAP rounds I am going to speculate that the Sherman crews where swapping with Hellcat units since they both use the same gun.

I suspect the shells were interchangeable however, see http://en.wikipedia.org/wiki/3in_Gun_M5 HVAP is listed as APCR-T

[Michael Emrys]

On the other point of swapping HVAP rounds I am going to speculate that the Sherman crews where swapping with Hellcat units since they both use the same gun.

I had the same thought this morning but hadn't had time to go look it up. But I think you might be right.

Michael

[michael Dwyer]

I had the same thought this morning but hadn't had time to go look it up. But I think you might be right.

Michael

:eek:ha ha, can I add that to my sig.