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The Unknown gun

L

Listy

Well-Known Member
Myself and a few others are researching WWII era military history. And we've recently stumbled upon a curiosity. It appears that this gun was actually made, but almost no records or information survive of it. we don't even know what it looks like. So I'm asking here if any of you can throw even a sparkle of light on the subject?

Our first clue was when someone reported that Rolls Royce had plans to take a 12Pdr gun and mount it on an aircraft as an anti-tank weapon, in the early 1940's.
Now like you we instantly thought it was the 12Pdr 12cwt gun as mounted on Royal Navy ships. However there was an issue, its give calibre was 70mm (2.75"), the 12Pdr 12cwt is 76mm. The book failed to give any more details.

The other thing that struck us as dismissing the 12Pdr 12cwt, is that its a fairly beefy gun, then I found this at an archive (Don't worry the archivist said these are government papers, and so under Crown copyright and that I was therefore free to post them).
Mounting this mystery gun in a early mark Valentine poses some interesting problems as it definitely rules out the 12Pdr 12cwt, as that's way to large a gun to fit in such a tiny turret.

Equally I found this performance chart. Which shows the performance of APCBC shells at 2200fps. Its interesting to see that it was tested at 1/4 worn barrel, which implies again that it was actually made. We also know that AP and APC rounds were made for the gun.

Past that we know nothing.

So if you've got any information, please stand and deliver, even if its some vague memory of something you read in a book some years ago. We really are dealing with an information dry patch.


Thanks.
 
Maybe a 12Pdr Davis Gun, although the velocity listed seems high for a Davis Gun. The U.S. mounted a 75mm gun in B-25's and used it for killing ships in the Mediterranean.
 
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This is mentioned in "Rolls-Royce Armaments" by David Birch, definitely worth looking for as it has loads of info on their gun projects. This states that a 12 pounder tank gun armament was being proposed, which R-R thought could be adapted for aircraft use. An MV of 2,200 fps is mentioned. The advantage of this was given as the ability to use the 6 pr's forging and mounting (which is of course what was subsequently done to produce the British 75mm tank gun). R-R were at that time working on a Type GA 6 pr aircraft gun which was said to be lighter and with less recoil than the 6 pr Molins (which implies a reduction in power); it seems that they were talking of modifying this design to fire 12 pr ammo (no details given, except MV planned to be 2,300-2,500 fps).

I suspect that the 12 pr tank gun project was superseded by the 75mm, which had the benefit of using existing US ammo. The R-R projects for 12 pr and 6 pr aircraft guns went nowhere (stayed on the drawing board I think), the RAF's focus being on a 47mm airborne anti-tank gun, with Vickers producing the Class P gun which was tested in 1946 when a pair of them were slung underneath a Tempest's wings.
 
We didn't know about the 6Pdr commonality, and your idea is certainly sound. It'll give us something else to look for in the archives, so thanks.

One thing that has bugged me though, the 12Pdr has the same rough performance on the 12cwt gun, but is 6mm lower calibre. Won't that lead to an unusually long shell?
 
There were 12pr 4 and 8 cwt guns that should be looked at re weight and size. Also recoil effect can be reduced by increasing the gun recoil travel to dissipate the energy over a greater time( Newtonian physics)
 
IIRC there's some more info on the tank gun plans in one of the books by David Fletcher (The Great Tank Scandal, I think). Unfortunately I'm in the middle of a reorganisation and this book is buried deep in a large pile....but if you don't have it, I'll try to dig it out.
 
Tony Williams said:
IIRC there's some more info on the tank gun plans in one of the books by David Fletcher (The Great Tank Scandal, I think). Unfortunately I'm in the middle of a reorganisation and this book is buried deep in a large pile....but if you don't have it, I'll try to dig it out.
Click to expand...

I've got Fletcher's full selection (Mechanised force, Scandal and universal tank), so I'll go have look.

Thanks 2 Pounder, we'll add it to the collection.
 
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