Someone needs to compile all the answers given to this questions from all the posts of it being asked and make a chart or something and posts it in fluorescent red at the top of the forum.
Early Virginia smoothrifle:
.615 bore preferred roundball loads;
80 grains 3f, thin card, lubed felt wad, .610 ball, 2 thin cards. I now really only use this when hunting a particular property where longer shots are more possible or even likely. I've since discovered the nicer and more economical shooting,
65 grains 3f, thin card, then the surprise,,,,, either a lubed felt wad and with .610 ball on top or a .010 lubed patch holding a .595 ball,,, they both shoot equally well, the ball with wad gets 2 thin cards on top. This is the only decent shooting PRB load I've found with this smoothrifle.
Decent shooting, acceptable, is under 4" at 50 yards, to me.
Centermark Fusil des Chase;
this gun with its thinner barrel and lighter overall build is a little fussing and a little harder kicking.
80/85 grains powder with a patched .600 ball shoots well, but feels abusive after a few shots, especially off a bench when load testing learning the loads hold overs/unders.
Current preferred load is; 75 grains 2f, dry felt wad, lubed wad (either felt or lubed ball of tow), .610 ball, two thin cards.
Ball of tow is about the same size as the roundball before I smush it into a nest and put it in the muzzle. It may shoot slightly better than the felt.
Groups in this gun tend to open up if a stiff or hard card/wad is placed between powder and ball.
I do intend to test with a nitro card instead of 2 thin cards over the ball because I had the ball lift a the cards a few inches up the bore during transport this year.