The case is 2 5/8, the tape is underneath the case flush to the base.
There 8 narrow grooves for the 1 in 52 inch twist rifling, the barrels are 28 inches long.
I think Daryl is right on, the chokes seem to have been removed a some point.
Mr Greener said this was defiantly one of their choke bore rifles, proof marks are from 1875-1887, he considers this to be a heavy (9 1/2 lbs) 10 bore made for round ball and brass cases.
I still have issue with primer fit, I am in Canada so buying brass from the US is a pain in the a$$ and not a option right now.
Tinker, why not 2 lubed fiber wads? does Colum height matter?