Dale - did you get the liners from Trackofthewolf or were they full barrels to start? Track's liners are hammer forged and finely finished inside. They'd be easier to fit to a 20 bore, though as 5/8" is a normal liner size. They do have some at 13/16" (.687")which is a bit smaller than 14 bore and a few at 7/8", (.875")a bit larger than 8 bore Unfortunately, they don't have any at 3/4" (.750")
; I've been thinking of tackling this job on my bro's new lathe. I was thinking of a fast twist .444 (or longer) in a 20 bore double for black powder equivalent loads for 400gr. bullets.