There is a load for SxS percussion shotguns I got from Muzzleloading Forum called "the Skychief load" which everyone who has used it swears gives tighter patterns for longer distances (no chokes on these guns).
-- powder
-- over powder card (.125")
-- Shot
-- overshot card
-- 1/2" cushion wad absolutely soaked in olive oil.
I keep my wads in colored plastic M&M tubes and use an old "dime coin dispenser" (mine is 16 bore) to dispense the OS cards.
I had the temerity to suggest using vegetable oil (higher burn point) and everybody jumped me saying not to mess with this formula. Apparently the olive oil keeps the shot bunched much longer.
https://www.muzzleloadingforum.com/threads/skychief-smoothbore-load-recipe.113195/The olive oil tends to ooze over the barrel a bit as you ram the cushion wad home. I keep a rag in my back pocket for the excess.