Hi Stellan:
Just to add to the confusion, Canada took the twin 20mm Oerlikon mounts made in Regina, Saskatchewan and modified them to mount single 40mm Bofors. The resulting hydraulic powered unit was called the "Bofin" or "Boffin" depending on who spelled it. It successfully served on HM Canadian Ships and as ground based airfiled air defences in Lahr and Baden-Baden, West Germany for many years. The army replaced them with the twin 35mm Oerlikon and the navy has put them back into service on our new fleet of minesweepers. Not bad for a gun made in 1942 (ish)! 62 years old and still going strong. To the best of my knowledge they are the oldest guns still in "frontline" service in the Canadian Forces.
The Ack-Ack tank drawing you posted is a twin 20mm version not a 40mm.
The Kerrison Predictor was a maze of gears and spinning bits that today is replaced by a small computer. For its time it was the cat's meow and remarkably improved the single shot kill probability of the 40mm. (SSKP is the statistical way we Bird Gunners calculate a gun's efficiency). I would dearly love to acquire a Kerrison Predictor to display with our 40mm. (see
www.calnan.com/swords for some photos of our gun at various exhibitions and parades). I have an original fitted tarpaulin for a Predictor... now I just need something to put under it!
We should see if Geoff will start a new category for artillery and let this rapidly growing thread become its first. :idea:
I will post all the various numbers for our two guns (the Bofors and the M1939)... perhaps you want to start a register.
I will also dig out what I can from my library on Canadian production so you can add it to the knowledge base... just bear with me as my library is currently housing all the furniture and boxes from my basement while I drywall and finish my new basement office and den!
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Cheers! Mike