Always locate your fire patches and "read them". If there is any burn-through, hole, or a shattered/consumed/blown patch, then your load or crown is not there yet. If I can see sunlight through my patch material when held up to the sun, I look for better patching.
Also, look for a sunburst scorch pattern on the patch, even if there is no burn-through. This means you are getting blow-by of the powder gasses. This is result in uneven velocities and lousy accuracy. If you see the scorch marks, you need a thicker patch, a bigger ball, or both.
If your patch is blown apart, your cloth is junk or the pre-lube is old and deteriorated the patch. You need stronger material.
Read up and Daryl's muzzle treatment, as a sharp crown will cut up your patches so they fail before you shoot them. Also, a smooth crown allows easier loading of a tight fitting load combo.
With the deep Rice round rifling, you'll need a thick (.018 or thicker) patch and a fat roundball to drive the patching into the grooves.
My Rice 50 likes 72 grains of Goex 2f, The Minute-Men .018 patching, and a .495 ball. Mine is flat bottom rifled, so you may need to go thicker on the patching. I might recommend a steel range rod as well for loading a tight load. Swiss powder is faster, so you may not want to go that route as it'll just make your situation worse.
Good luck.
God Bless, Marc