I can remember a few guys that travelled with the Fairgrounds that travelled around the country in the fifties having something similar that fired a .22rf cartridge.
I remember asking one of them where he got it from and he said he made it and after a couple of shots chucked it away !!
Obviously made from 'monkey metal' so not as professional as the one being discussed here.
Unless he chucked it away after using it for something nefarious and wanted rid of the evidnce, I never thought of that at the time