I’ll go along with Tomme on the 180 gr K-31. If the nose was widened from .297″ as it is now, to about .301″, it would be perfect for the .308 Winchester. The length at 1.085″ would be just right to fit in a standard M1A/AR-10/FAL type .308 magazine, and still keep the gas check within the neck of the case. It looks like an almost ideal design for the .308 Winchester, other than the nose diameter being too small.
If the whole cavity was orbited out .004″ larger, what effect would that have on the gas check shank area of the bullet? I think I’d be more concerned about that than I would about sizing the bullet down from .315″ to .311″.
I would rather have a purpose made design with the cherry cut to make the bullet the proper size in the first place. I’ll sign up for one of those right now. Put me down for a 4 cavity.