If the bore is .729 it would be considered a papercase gun but could be shot with brass cases. The bullet matches the bore of the gun. As Curl has stated once the size of the bore/bullet increases, it gets to a point on any given gauge where if you seat the bullet into a papercase it bulges the case and that bullet/case cartridge combo will not enter the gun. Bore diameter dictates which case you need in any given gauge rifle.