I'm in the process of case forming for a .257 wildcat based on the .308 Win case. It requires a longer neck and steeper shoulder than either .260 Rem or a .243 Win basic case. It forms well with necking down a .260 Rem case but I would rather use a Norma or Lapua 243 Win case. Problem is that it won't neck up without leaving the oversize "ring" at the base of the neck. This even happens when I expand the .243 neck to .258 in a previous operation. What to do?

I presume you haven't loaded and fired any of the rounds as yet? If not, do so. The ring may come out, as it does when fireforming.

Strangely enough, the ring is just big enough to keep me from chambering. I'm thinking that I may have to expand these necks up to .264 just to neck them back down?