[@Oni_] high end, expensive pepper boxes can be enchanted to turn automatically, or use a mechanism to rotate the barrels. Alternatively you can use magic to turn the barrels if you have the aptitude. But cheaper low end pepper boxes will generally be turned by hand -  though for the rp, keep in mind that a vast variety of the monsters in the new world appear very resistant to conventional shot and powder weapons. Those are more to fend off animals and other people.