I have a sweet little .36 cal Seneca and ordered everything to make a .45 cal drop in round ball barrel for it. 36" Green Mountain barrel 13/16" across the flats, with 1:60 rifling. Breech plug, front & rear sights, T/C under lug, under rib, and steel thimbles. It should all be here in the next couple weeks.
I think I may have to shorten the barrel to maintain balance. I'll see after everything is fitted with the exception of the under rib and thimbles. The under rib and thimbles will be silver soldered on. I did it with my .54 cal and they're solid as a rock.
I may keep it longer seeing as .45 cal Seneca's are prone to cracked stocks due to the .45 recoil. Depending on how it feels. Maybe the extra weight may help, but I don't plan on shooting heavy loads out of it either. My winter project.
I blame it on my wife for getting me a new Century 24 Gun safe for Christmas. It will go perfectly beside my 18 Gun Sentry.