Lovely! Agreed. Measure the bores first. Defiantly a round ball gun. The undersize ball in a shot cup does work (not sure how a patch would work in practice). A .690 ball drops though the barrels. Consider a .735 ball without a shot cup if your measurements work out. A fiber wad behind the ball will seal the bore. Would be curious if yours appears to have three very subtle "lands" in the barrels. Congrats!