I've been looking for suitable J-words to feed my .256 Win Mag Marlin with little luck. But I think I still have a couple thousand factory .251 j-words intended for .25 ACP. How much of a chore would it be to bump those up to .257? As I recall, they have pretty thick looking jackets! I've never done any swaging other than cases. Are there machinists here that could make such a die?