savage,
i wasn't trying to be a wise guy, but i thought i missed something. i'm all about a new project, and sometimes less is more. i like the .221fb cartrige, but it seems easier to download the .223. than to go to all the trouble making it work where the .223 allready rules.
how about a tac. .20 ? that seems like a cool project. kind of a .204 ruger on steroids in a ar-15 platform. if interested, go to saubier.com
good luck
p.s. a friend has a savage bolt gun with shillen barrel in .221 fb. that shoots in the 2's on a calm day.