British "75mm AT gun"...

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Paul_G_Baker
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Re: British "75mm AT gun"...

Post by Paul_G_Baker » 28 Aug 2012 17:15

Knouterer wrote:
Paul_G_Baker wrote:
Clive Mortimore wrote: ... 100 old 3-in 20-cwt AA guns were collected, provided with a special 12 1/2 lb shot, and mounted half in Churchill tanks and half on 17-pr carriages, the production of which was in advance of that of the guns. ...
That surprises me. I thought that initially the production of the guns was in advance of that of the carriages, and that for that reason a number of 17 pdr barrels were mounted on 25-pdr carriages in North Africa?
You're right about the 17/25pdrs - there is a photo of one of those! The 3in 20cwt on a 17pdr carriage is more of a mystery; but it is just possible that there was a holdup in A/Tk gun barrel production (for example, while producing 17pdr guns to fit into tanks) which could account for a temporary surplus of carriages!
Paul

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Re: British "75mm AT gun"...

Post by Clive Mortimore » 28 Aug 2012 20:32

Paul_G_Baker wrote:
You're right about the 17/25pdrs - there is a photo of one of those! The 3in 20cwt on a 17pdr carriage is more of a mystery; but it is just possible that there was a holdup in A/Tk gun barrel production (for example, while producing 17pdr guns to fit into tanks) which could account for a temporary surplus of carriages!
Hi Paul

It was you who referred to the Pemberton report I will repeat my querry regarding this report and the dates.

"What does seem strange that in the Pemberton report the carriages were well in advance of the guns in April 1941? The 17 pdr was not approved of until May 1942 and to get it into action as soon as possible where the guns that were advance of the carriage production the guns were mounted on 25 pdr carriages. So the carriage building programme must have been slowed down from April 1941, before the approval and September 1942 when the first 17/25 pdr was test fired."

It appears that the Pemberton report is the main source of the information of these 50 3 inch 20 cwt guns on 17 pdr carriages and he states that their conversion was approved in April 1941, one month before the end of the Blitz when all available AA guns were needed according to Colin Dobinson in his book "AA Command". Did the civil servants responsible for ordering anti tank guns know something that the AA Command and RAF never knew?

I am not too sure of the concept of the production of the tank gun barrels delaying the production of the towed version barrels. The Mk1 was the towed version, it differed in how it was attached to the recoil system compared with the other maks used in the tanks. The MkII, MkIV, MkVI and MkVII were tank guns, with Mk V for the US M10 GMC and the MkIII was the Royal Navy version on the LCG(M). I am sure the Royal Artillery would have been impressed with an inferrior gun on a heavy carriage after they had been issued with the 17 pdr.

Clive
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Paul_G_Baker
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Re: British "75mm AT gun"...

Post by Paul_G_Baker » 29 Aug 2012 12:08

Clive,
You wrote:It was you who referred to the Pemberton report
I did; although I found the reference to it (and the quote from it) on another board, I appended the link in that post. I have not seen a copy of Pemberton's report myself.
It appears that the Pemberton report is the main source of the information of these 50 3 inch 20 cwt guns on 17 pdr carriages and he states that their conversion was approved in April 1941, one month before the end of the Blitz when all available AA guns were needed according to Colin Dobinson in his book "AA Command". Did the civil servants responsible for ordering anti tank guns know something that the AA Command and RAF never knew?
The 3in 20cwt had been in process of being phased out of front-line service in favour of the more modern 3.7in since the begining of the war; which would imply that there were surplus guns about in the UK. The 3in would (IMO) also be being made increasingly ineffective due to both the higher altitude of attacking aircraft and the change to night bombing.

One would also have to factor-in any spare barrels held in storage for rapid replacement - as ex-military, you would be able to estimate the numbers better than I, but some or all of those putative barrels could well have been released for special projects on the basis that the weapon was soon to be withdrawn from the A/A role.

In addition, the stowage diagrams for the Gun Carrier seem to show a weapon fitted with a screw breech - while the text descriptions that I have seen quote the guns as being Mk 1 (which were all, according to Hogg, vertical sliding block)! So, either the artist got it seriously wrong, or the Gun Carrier Weapons (and, by extension, the second 50 - which were also originally intended to go into Gun Carriers) were not Mk 1 guns at all! How effective would screw-breech guns have been in the A/A role?
I am not too sure of the concept of the production of the tank gun barrels delaying the production of the towed version barrels. The Mk1 was the towed version, it differed in how it was attached to the recoil system compared with the other maks used in the tanks. The MkII, MkIV, MkVI and MkVII were tank guns, with Mk V for the US M10 GMC and the MkIII was the Royal Navy version on the LCG(M).
The recoil system only attaches to the breech ring, does it not? The actual gun tubes would probably be absolutely identical, just made up (in a removable way - the Centurion Tank's gun tube seemed to screw directly in) to different types of breech rings - and therein lies my thinking about the cause of a possible delay; the production of gun tubes being limited by the capacity of the available rifling machinery sets.
I am sure the Royal Artillery would have been impressed with an inferrior gun on a heavy carriage after they had been issued with the 17 pdr.
The idea of utilising the 3in 20cwt seems to have sprung from an intelligence report that the Germans were ready to field 90ton tanks (IIRC), at a time when the 17pdr wasn't ready. It's an improvement on the 6pdr, and (for an emergency lash-up to give the troops something to shoot back with) not that bad an idea. If only there was a photo to confirm that it was built - but there don't appear to be any photos of one weight of the 6in howitzer trio, either (as far as I have been able to see), and no one seems to doubt that that variant existed!
Paul

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Re: British "75mm AT gun"...

Post by Clive Mortimore » 30 Aug 2012 00:11

Paul_G_Baker wrote: The 3in 20cwt had been in process of being phased out of front-line service in favour of the more modern 3.7in since the begining of the war; which would imply that there were surplus guns about in the UK. The 3in would (IMO) also be being made increasingly ineffective due to both the higher altitude of attacking aircraft and the change to night bombing.

One would also have to factor-in any spare barrels held in storage for rapid replacement - as ex-military, you would be able to estimate the numbers better than I, but some or all of those putative barrels could well have been released for special projects on the basis that the weapon was soon to be withdrawn from the A/A role.
In 1941 the 3 inch was still in service both with the Heavy AA Regiments and the Light Regiments due to the shortage of 3.7 inch and 40mm guns.

The Royal Navy still had just over a 1000 on board various ships at the start of the war, most were still on board a vessel at the end. 10% had been lost or stricken by 1943. I think any spare barrels would have been handed over to the navy as they used all the Armys Mks as well as some of their own, Naval Weapons of World War Two by John Cambell.
In addition, the stowage diagrams for the Gun Carrier seem to show a weapon fitted with a screw breech - while the text descriptions that I have seen quote the guns as being Mk 1 (which were all, according to Hogg, vertical sliding block)! So, either the artist got it seriously wrong, or the Gun Carrier Weapons (and, by extension, the second 50 - which were also originally intended to go into Gun Carriers) were not Mk 1 guns at all! How effective would screw-breech guns have been in the A/A role?
The screw breach would not have been a problem, like that of the 18 pdr and the French 75 it was a single action therefore quite cabable of high rate of fire. All Mks fired the same ammunition.
The recoil system only attaches to the breech ring, does it not? The actual gun tubes would probably be absolutely identical, just made up (in a removable way - the Centurion Tank's gun tube seemed to screw directly in) to different types of breech rings - and therein lies my thinking about the cause of a possible delay; the production of gun tubes being limited by the capacity of the available rifling machinery sets.
The recoil system does not only attach to the breach ring. Many guns have a breach collar that the recoil ssytem attaches to so the breach ring can be removed and then the barrel removed, keeping everything else in place. Some older guns had a casting on the barrel sleave that attched to the recoil system. There are guns where the breach ring does attach to the recoil system, the 3 inch being one of these.

The idea of utilising the 3in 20cwt seems to have sprung from an intelligence report that the Germans were ready to field 90ton tanks (IIRC), at a time when the 17pdr wasn't ready. It's an improvement on the 6pdr, and (for an emergency lash-up to give the troops something to shoot back with) not that bad an idea. If only there was a photo to confirm that it was built - but there don't appear to be any photos of one weight of the 6in howitzer trio, either (as far as I have been able to see), and no one seems to doubt that that variant existed!
The 17 pdr wasn't ready, so why was the carriage chosen for these guns? The idea of using the 3 inch came about in 1941, the 17 pdr was still under development so would 50 "spare" carriages would been avavilable? This brings me back to my argument that either a new saddle design was made to fit the cradle of the 3 inch gun or a new breach ring was made to fit the 17 pdr recoil system. Both would have been major design changes. To get them into production in 1941 without any approval would have been quite hard.

Clive
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Re: British "75mm AT gun"...

Post by verdenpark » 30 Aug 2012 06:25

Is this 3" 20cwt. the same gun as the Navy's 12pdr. 20cwt. QF Mk.I, or is it a different animal?
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