Polstens made by John Inglis

Does anyone know what date John Inglis commenced the production of 20mm Polsten AA guns, if indeed they ever did? I have been reviewing various documents from Kew on Polsten manufacture, and there isn't even a hint in any of them that Polstens were to be made in Canada.

I know that Inglis made a quad Polsten mounting, allegedly with guns they had made themselves, but I am starting to wonder whether in fact the guns were imported from the UK.

 

I tried to do a little digging and found what might be a clue. I know this is an online game forum post, but the fellow actually cited his sources.

"Meanwhile, John Inglis and Company were in the process of designing the Inglis 20mm cannon, a gun built around the Hispano-Suiza 20x110mm round. This gun would be "superior not only to existing allied models but also to the German 2cm Flak 38."[3] Drawings were completed in April 1942, and a automatic test fire was completed in September 1942. In February 1944, the Inglis 20mm gun met Directorate of Development of Vehicles and Small Arms standards. Simultaneously, development was underway on the Inglis quad mount, a system which would carry 4 20mm Inglis guns in an hydraulically operated turret. The system displayed minimal movement while firing from the high mobility 6x6 chassis. However, the Inglis was doomed as the 21st Army Group changed its policy regarding 20mm ammunition, dictating that its supply chains would no longer support Hispano-Suiza ammunition. This notice was received in February 1944. In response, the quad mounts had to be modified to carry Polsten guns, instead of the original Inglis guns."

F60S (20mm Quad Polsten) for 3.0 Canadian (UK/Commonwealth) SPAA

 

Part of an article from the Montreal Gazette 20 September 1945:

 

I wonder if the Inglis was also the gun intended for the Skink? I've previously read (probably on Wiki) that the delay in producing the Skink was down to 21 Army Group insisting on Polstens instead of Hispano-Suizas, which necessitated a redesign of the turret.

But it would make more sense if the Skink had been designed around the Inglis guns, because Hispano-Suizas would have been a very odd choice for fitting in a tank.

 

Thanks very much for this. I'm wondering when Canadian production commenced, as UK production was severely delayed, and didn't begin until about October 1943.

If the quad mountings designed by John Inglis had to change from Inglis guns to Polstens due to an edict from 21 Army Group (which I suspect happened in late 1943), then I would guess that Canadian production of the Polsten did not begin until the second quarter of 1944 at the very earliest.

 

There's a whole page article on C.D. Howe's (Minister of Munitions and Supply) to Parliament in March of 1944 in the National Post (March 25 1944). The article's worth a read but the smallest I can get it is 7 MBs. If you want it send me an email address to send it to. The part you might be interested in:

Regards,

Dave

 

Some discussion in the below linked report on the 'Progress of Equipment' of Canadian Forces overseas;

https://www.canada.ca/content/dam/t...yhistory/dhh/reports/cmhq-reports/cmhq141.pdf

There used to be a typed PDF of the report that was searchable, discussion on the 20-mm equipment is at paras 23 to 28. There are also entries in the index to contents of various CMHQ files (index is in C-5770), which involves sustained trawling to get to what sounds interesting (sometimes it is, sometimes is ain't...).

Canadian Military Headquarters, London : C-5770 - Image 1 - Héritage (canadiana.ca)

Gary

 

Thanks for this Gary - it's a keeper. It does suggest that it most likely was Hispanos that were fitted to the Skink. Also the idea that the Canadians were ordered by 21 Army Group to adopt the Polsten is somewhat awry - the Canadians seem to have made this decision themselves as a rationalisation exercise.

 

Thanks very much, Dave - I'll be keeping this as well. I've poked around in my own files and have found an entry on Canadian Polsten production, below:



A couple of things worth noting were that as far as the British knew, Canadian Polsten production had not commenced by the middle of April '44, and that the Polsten requirement was being cut at this time anyway. I'm not sure if this was an intimation that they realised that the Luftwaffe were a spent force even before D-Day - but it might have been.

 

The following extract is from my new book: Autocannon: a History of Automatic Cannon and their Ammunition, which is published by The Crowood Press: Autocannon - The Crowood Press

(With assistance from Roger Lucy)

20MM INGLIS MODEL EX-1–5000:

20 × 110 HS or 20 × 110RB AMMUNITION.

This project commenced early in 1942 with a proposal from the Canadian Army that the country should develop their own 20mm AA gun. The initial request was for a gun similar to the Oerlikon Type SS and using the same 20 × 110RB ammunition, but with a quick-change barrel, belt feed (interchangeable between left and right side), and a much higher rate of fire (700–800rpm). However, the ammu- nition soon changed to 20 × 110 HS (Hispano) as that was the British Army’s preference, and approval was given for Inglis to commence development in the spring of 1942. Progress was rapid, with the first prototype being tested in autumn of that year. After a period of trials and modifications, an initial batch of 58 guns was ordered in spring 1943, of which 41 were delivered. The guns passed their firing tests, albeit with 50 and 100-round magazines; belt feed was expected to be ready in autumn 1944. Single and quad mountings were developed (the latter featuring powered traverse).

However, in February 1944 the British Army changed its mind again and decided that all future 20mm AA guns would use 20 × 110RB Oerlikon ammunition. The Inglis gun was redesigned once more and performed well on test, but by the time it was ready for production, there was no longer a requirement for it. The mountings were adapted to take the Polsten instead.

The Inglis gun had a mixture of the characteristics of other cannon. It took the hybrid gas/blowback operating system from the Hispano, the quick-change barrel from the Oerlikon, and elements of the cartridge feed from Hotchkiss. It was also given an integral cradle to support the gun. Data for a belt-fed gun using HS ammunition include a weight of 68kg, an L/62 barrel, and a rate of fire of 700+rpm. In the magazine-fed version, the loaded weight of the scroll-type magazines was 37kg for the 50-rounder, and 61kg for the 100-round magazine (as shown).

 

My eyesight isn't the best - but this photo has always intrigued me.

The mounting is traversed to the left (of the gunner) and part of the inside of the far side is visible.

Why is it that the guns on the right hand side of the mounting seem shorter than those on the left. Are they not mounted on the same trunnions? Or are the right hand guns out of battery (or partially out of battery)? Or maybe it's my eyes!

christian