A thought ( probably not worth the time typing it out?).
On the introduction of the Firearm Certificate in the UK for rifled cartridge arms many Rook and Rabbit rifles were bored out to .410 shotgun for which no Certificate was then needed.
Whilst that seems sad now it at least saved them from immediate destruction. Many were not, however saved from the combined effects of the late introduction by Eley in the late ‘50s or early 60’s of non-corrosive .410 cartridges and an apparent reluctance to clean .410 guns.
Many are now deeply pitted, both in chambers and bores. If they retain the original barrel profile they can be worthy candidates for re-lining to an original or modern small game round such as .32/20.
Others have had the forward portion of the barrel tapered or turned down. They may well retain enough metal to clean up to 32 bore if nor to ( more sensibly) 28 bore.
All of which is likely to cost far more that buying a brand new .410 Baikel. As I said at the start ....
