Howdy Doug: Really aiming for a muzzleloader, but thanks for the info on Appleton's GP actions. Gad: More choices!
Anyway, I would be happy with a 12-bore single that would handle the 835-grain NEI cottonspool, second from right, or the mystery 1100-grain semiwadcutter at right, over 6-7 drams. These two are left over from my brief but passionate fling with a Pedersoli Kodiak .72 double.
(Hope the photo works)