Depends which smoothbore I'm shooting. Both 20 gauge with slight difference in actual bore measurement.
One gun likes 80 grains 3f, a .600 ball with a lubed. 010 patch. The other barely groups with that load. The other likes 80 grains 3f, but only shoots looser ball combos well. Best load at this powder charge is 2 thin "overshot" cards on top of the powder, then a lubed 1/4" felt wad, the ball, topped with 2 more thin cards. At 50 yards I can cover all my shots with my hand.
Recently I did some experiments with lighter loads to try to comply with a local club's rules for their trail walk.
Turns out that with 65 grains 3f the same ball and wad combo shoots just as well out to 50 yards as the 80 grain load. But, also shoots a .595 ball just as well either patched or in a paper cartridge, or using lubed "faux tow" instead of the felt wad.