NitroX,
A 458Wmag has a belt of .02" to stop the case. I have .026". If I leave the shoulder a couple thousand forward I can't jam the bolt closed. Would I take a factory chamber, dies, brass etc probably not. Custom chamber with dies made to my fireformed brass I've never had an issue. I did have to open the rails up to get a perfect feed with the more or less flat nosed 400s.