THS:
I believe most reloaders make them out of .30-06 cases.
Much cheaper if you're not in Australia, and you don't have to worry so much about case-life.
All you need is a tapered expander-ball in your .318 sizing die, although most expanders could easily be ground to work fine.
Trim as necessary.

Also, why full-length resize? Just resize them to fit your chamber, and case-life is a non-issue.

Welcome to NE.com, BTW.