I'm already using the thinnest patch and I still have to use a mallet to start it. I can use a smaller ball for a given caliber?!?!?
Yes.
The difference between bore size and ball size is described as “windage.” Old-time military muskets may have had as much as .050” of windage. With a ball that much undersize, you’ll get a lot of blow-by, which will cost you in terms of velocity and energy. Also, and this may be just theoretical, the path the ball follows as it travels toward the muzzle may not be concentric with the bore, so it will likely lose accuracy. In my own experiments with undersized balls, I found excessive and rapid fouling buildup, also. This was with loose wadding.
I would suggest you try the ball you are using, following
@The Crisco Kid ’s formula, using a nitro wad to protect the powder charge from grease, a lubed wad, bare ball, and a card wad to hold the ball in.
As for myself, I just use a smaller ball with a lubricated patch, like a .595” ball in a 20 gauge, and whatever patching material is handy.
What gauge or caliber is your gun, and what is the diameter of the balls you have been shooting? Bear in mind, undersized bores are not unknown, meaning that the actual measurement of your bore may be smaller than the stated size.
Best regards,
Notchy Bob