17-pdr Sexton / 3 inch Ram SP

[Hanno Spoelstra]

Interesting tid-bits found on AFV News Discussion Board, copied here to save this information which was new to me:
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Origins of 17 pounder
Posted By: Roger Lucy
Date: Sat-Nov-19-05 at 14:26 hr

In Response To: Re: Detailed ref sources on ballistics of 17 pounder & M1A1 76mm guns?

According to Hogg's British and American Artillery of WWII the 17 pounder arose from a meeting held at Adelphi House London on 21 November, 1940 to examin a heavier replacemenet fort the 6 Pounder. Calculations showed the best solution was a 3 inch gun firing a 17 lb projectile. Design was done by Armaments Design Dept, and - despite the Director Royal Artillery's misgiivngs about the size and weight of the beast - the first 4 pilots ordered in July 1941 with different barrel designs. After trials to determine the best design the 17 pdr was approved for serive on 1 May, 1942. Due to delays in finalizing the design of the carriage and need to have something to counter Tigers, the interim version on a 25 pdr carriage was test fired in Sept 1942 and the first exasmples sent to North Africa later that year.
Design of the Archer SPAT seems to have begun about the same time, as an interim to producing a tank mounted 17 pounder armed Tank (A.29 or A.30) and the concept approved by the Board of Ordnance in February 1943. However the first trials version does not seem tom have been ready until March 1944 and it did not reach the troops in any numbers until October, 1944.

According to a October 1942 correspondence between the Deputy Director General of the Canadian Army Technical Development Board J.H. Crang, and the Departmnet of Munitions and Supply, the M10's designers had taken into account the possibility of mounting the 17 pounder anti-tank gun in it. During an April, 1943 visit to the UK, Crang provided the Director Royal Artillery, General Eldridge with a simple design fix that would allow the 17 pounder to be mounted in the M10 using the exisitng 3 inch gun's buffer and recuperator. He also provided a designg for 17 Pounder SPAT based on the Canadian Sexton 25 Pounder SP. Unfortunately General Eldridge showed no interest in either proposal. Crang however left a copy of his drawings with the British Directorate of Tank design at Chobham.who passed a copy to the Woolich Arsenal - which by applying Crang's solution successfully fitted a 17 Pounder to an M10, using only 200 man-hours of labour, and successfully proof-fired it on 22 December. Hence the Achilles. Its a pity the idea of a 17 pounder Sexton was not followed up. Its Ram chassis would certainly have been a superior platform than the Valentine chassis of the Archer - needing miniumal modification from the Sexton, it could probably have been fielded sooner, it would have been faster, the gun would have pointed the right way round and it would have had automotive compatibility with the M4 and M10. I suppose, in line with British naming practices, it would have acquired an ecclesiastical name begining with "A" - Acolyte? Archdecon? Archimandrite?
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3 inch Ram SP

Posted By: Roger Lucy <Send E-Mail>
Date: Sun-Nov-20-05 at 16:35 hr

In Response To: 17 pounder Sexton (Paul Roberts)

Actually it was copy of the M10 built on a Ram chassis. In the summer of 1942 the Canadian Army Overseas wanted an example of the M10 to test. As it was only just being introduced in the US it was not possible to obtain an example, but US Ordnance provide the drawings and facilitated Canada onbtaining an M10 turret with 3 inch gun from the Fisher plant. The drawings were received on 29 August, 1942 and the Army Technical Development Board approved its construction as Project 35 on 3 September.
A Ram Mk.II chassis was assigned to the project and the Montreal Locomotive Works modified the hull along the general configuration of the M10, except driver’s hatch was placed on the right side, and the engine hatch was adapted to the Ram’s Wright petrol engine). The project was not given a very high priority, assembly only began on 23 October, and due to delays in getting the turret, it was only finished in December. The completed vehicle was then sent to Petawawa for trials, and was then shipped to the UK, arriving in March 1943. Trials were held at the Larkhill Artillery school in April. The M10 turret's lack of a power traverse made it very difficult to operate on slopes over 10o An effort was made to install a power traverse from a Ram I, but this failed due to the turret’s poor balance - either a heavier counterweight or more powerful traverse were required.
On 21 June further trials were suspended. The M10 was in full production, the UK had acquired 1,600 and the first vehicles had already arrived there. It had never been the intention to put the 3 inch Ram SP into production, the whole purpose the project had been to produce a working “mock-up” for the CAO to evaluate. The vehicle remained in the UK at the Canadian Artillery School.

The idea of a 17 Pounder Sexton was on of Lt.General Andy McNaughton's many inspirations, this one occuring in December 1942 (of course the Sexton was not yet called that). Some paper studies were made which validated the idea, it then bounced between Canadian Military HQ and the War Office for six months before the Brits finally said they were not interested. More on this and other projects in my forthcoming "Secret Weapons of the Canadian Army", which should be available from Serive Publications (www.servicepub.com) sometime next year.