Do a search in this double rifle gunmaking forum.

Alan McKenzie posted a photo of a .410 shotgun made into a rimfire in WA.

Baily Bradshaw had at least one thread on a .22 rimfire (?) and maybe a .22 Hornet (?), with a from scratch double rifle build.

Maybe another thread too.

A .22 Hornet Double rifle would be cool and I project I would still like at some point to look at myself - though not me building it!