I suspect it would be easier to download some .233rem rounds to get the velocity you want.
I have seen .223 cases where the body was essentially solid, with just a small diameter hole drilled through from primer pocket to a conventional neck that held the bullet.
This gave a case with a much reduced internal volume, but which otherwise functioned in the same way..
I have often wondered if you could achieve the same thing by inserting a small copper tube through the existing case and using JB Weld to fill up the void around its exterior...
Regards,
Peter
Last edited by Pete E; 11/01/09.