Wildcathunter,

I would sure guess it would work to form .257 AIs, since the case length and powder space is pretty similar to the 6.5 CM--but the only way to tell for sure with COW forming is try it. (As I've noted before on here, there is no handloading manual of COW loads!)

“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck