Rimfire cases for loading???
Though I can see some applications, this doesn't really appeal to me. I just wonder WHERE THEY CAME FROM? This is the first time I have seen anything of the sort. Is there data out there? I would suppose they would be useful for necking down to .17, or something like that. It just fascinates me, the things people can come up with!
Ebay link-Rimfire cases

Years back I saw primed rf cases for some of the obsolete cartridges for sale. They made some sense.

Back in the 1880's up to about 1920 empty rimfire cases were available for loading. I believe several of the fancy target rifles were loaded with a rimfire cartridge with powder and an overwad. then a false muzzle was placed on the rifle and the paper patched bullet was forced down the barrel engraving the rifling. I believe Harry Pope thought this was the best method for target accuracy. I owned a Pope barreled single shot many years ago with a false muzzle and an old timer told me this. (He was 80+ years in 1961) I have seen references to this in books saying it was done with center fire too.

A fellow by the name of Fred Hunnington used empty(spent)rimfire cases and swaged them into a bullet. In his backyard shop,he developed a press for doing such. His friends all wanted one of the presses. He had a love of shooting rock chucks. So he called his press the Rock Chuck Bullet Swage. Better known now as simply RCBS. It ends with it--but thats no BS.