Don't take it wrong but if I was building a 257 weatherby, it would have a 7mm Rock 8.5 twist in a #3 contour and have a 7mm remington chamber with a bit longer than normal throat. Been the Roy route, fun, but for longer range stuff the bigger pills served me way better.
I have had several 7mm's of various flavours including the mighty Mashburn (which eats up 7mm RemMags like cotton candy), and could have gone this way or to any other H&H or 404 based case with my FN now being re barreled. I am building another 257WBY. For deer and Antelope with some occasional varmint shooting, it is just very hard to do any better than that round. My last mule deer kill was from 618 yards out. Nothing else would have put more meat in the freezer than what is in there right now, and I do have larger rifles in the safe.
Since you are going WAY off base with your build idea and input from the OP's query (bad form and taste, IMO) I will offer that all of my 257WBY's have been built on either a CRF model 70 or some variation of a Mauser in Chrome Moly steel with nice wood for a handle. Including my now in proccess 257WBY on an FN. And that these various 25 Roys have downed a freight train load of deer from close to quite distant ranges. Sometimes just right is... well, just right! The 257WBY is one of those IMO. Part of the appeal is that the 257WBY does not recoil much. VERY easy for most to shoot really well and with proper bullets and loadings, lazer beam flat. In short, the 257WBY is just plain FUN to own and shoot.
