RE: 257 WBY Mag ammo??
I owned two .257 Weatherby's. A mark V and a custom mauser! The custom mauser outshot the mark V and neither of them showed me that they truly offered me more than a .25-06 I owned. Ammo is hard to find for the weatherby and unreasonably priced!!
I doubt seriously if you could tell the difference between a .257 Wby and a .270 Winchester sheep hunting.
I used the mauser in .257 Wby on prairie dogs once.....NOW THAT'S SPECTACULAR!!!