Chokes make loads easy. My 20 flinter has about an Imp. CYL choke and I use normal or standard wad column. It shoots modified patterns.
It just does not do well with round balls at 50yards or further.
Had to edit the choke. Bit dyslexic, I guess. Was thinking about it's patterns when I was typing Imp Cyl., came out Imp. Mod.
Rich- I have had some luck with the heavy wet wad over the shot, but the thin cards between powder and shot seem to work in them all, Ml. and Ctg. with BP loads- cykl., or choked.
My SxS 12 had cylinder bores & I patterned it, both barrels. Thin cards won. With the Skychief load, the left barrel shot tighter than the right. With the 2 thin cards in between, both barrels shot about the same as the Skychief load, but more evenly.