Or a wartime attempt to use it when the common sizes were in short supply. anything would have been of use when cats and rats were the only meat available (Overworked draught horses excepted)
That would be a plausible possibility if it was a single one-off large calibre pistol. But two at once?
Vintage Airguns Gallery
..Above link posted with permission from Gareth W-B In British slang an anorak is a person who has a very strong interest in niche subjects.