While I understand the theory behind not crimping for rounds used in single-shot guns, I strongly recommend crimping, if at all possible, as well as insuring the bullet is tightly held by the case neck, especially with smokeless loadings! Both crimping and a tight neck interference help insure there is enough delay in shot-start to insure proper ignition of the powder. Failure to get good ignition can result in hangfires that can even result in overpressures if the bullet stops in the forcing cone or somewhere in the barrel. For jacketed Hornady bullets, I used to apply a new crimp groove using a knurling tool. May not be necessary with cast bullets as a light crimp can be applied that will actually compress the bullet side sufficiently to hold the slug in place.