Shooting patched roundballs will not harm the rifle at all. Even though it has a fast twist barrel, many of them will shoot roundball very accurate if you reduce the powder charge to lets say... 50 grains of powder. If you push the ball to fast it skips the rifling and down not get the spin on it. I shoot a Knight Wolverine with a fast twist. I shoot 40-50 grains of loose Pyrodex RS and a patched roundball with some amazing accuracy. Although I have found that long distance shooting the accuracy falls off. Whether that is caused by me, the rifle, or the low powder charge I can not say. But out to 50 yards it does real well. Try it, it might surprise you.