I dont know if anyone else has this same problem, but is seems that in hand loading if you use the 454 cases that the 460 does not like the slower burning powders. I think it is that the time that the bullet is traveling in the chamber not create the same pressure build up that would be generated in a 454 chamber. I could be wrong however i do not have this problem using the same powder and bullet in a 460 case loaded to 460 specs.