It is a .323 diameter I believe that is what the S in 8x68s is designate. Your right about the 8mm in the US it never really got off the ground. My gunsmith wanted to take it to Africa a few years back he said it is somewhat popular there and you can get ammo for it there if needed. Not sure what part of Africa he was talking about.
I bought it from an Old buddy of mine years ago because nobody ever heard of a Weatherby in that caliber back then, I thought it was pretty cool back then and still do.