If I read the info correctly that was linked to this rifle it is 45cal. If that is the case I would guess that the 290gr bullets are a little longer than your rifle will like. From my experience, when you get over 275gr the bullets will start to keyhole. The rifle should shoot round balls or something like T/Cmaxi fairly well. Only change I would make in the suggestions you have recieved is start with around 60gr powder. When I shoot patched round balls, my load is best at 60gr, is ok at 70 and goes bad really fast after that. If I read the info correctly it is also made in 32cal. If so, I assume your barrel is 7/8 across the flats. 7/8 barrels usually are not ment for heavy powder charges. Beautiful rifle.