Well, I sure wouldn't want to be stuck with WR ammo. The several batches I shot up in .500/.416 were among the worst factory ammo I've ever fired.

Max rim thickness for the .500/.416 is .040". What do the rims of the other brass measure? If they're .040" or under, then the rim seat was probably cut too shallow. I got a call from a guy with a new Westley Richards droplock with the same problem. Since the .500/.416 also has a shoulder, the problem could also be there, but probably isn't. Either way, it should be a simple fix. If you can't get Blowzer to do it, send it to J. J. Perodeau in Enid, OK. He fixed a similar problem for a friend of mine.