In fast-twist barrels, you have to use relatively light loads. The reason is that heavy charges cause the ball to strip, and unless it spins, accuracy is as bad as or worse than you'd get from a smooth bore. many European and English rifles had fast-twist barrels, like this Dixie Jaeger, and they were invariably loaded withlight charges. English guns for large or dangerous game, which were loaded with heavy charges, used very slow twist barrels, like 1/120"!!

Keep yore powder dry!!