You need to use less powder. If you find a charge that works it will be more critical of variations in charge than a slower twist barrel. Basically it will works but a slow twist is generally more accurate and more forgiving.

a ball will tend to strip with fast rifling and heavy loads.fast twist barrels also have shallow grooves for easier loading of conicals and sabots,whereas ball barrels tend to have much deeper grooves to aid in gripping the patch material.balls do best with around a 1-70 twist while conicals do well with around a 1-48 twist and sabots are somewhere in the 1-20 twist area.
you can used fast twist for balls if you cut your powder charge down,my TC white mountain carbine would shoot balls well with around 30 grs of fffg,while needing around 80 grs of same for either conicals or sabots.
Some guns may shoot fine with balls no matter what the twist or charge.