I hate this. OP wants a .257 Weatherby. How can you gun guys not understand this? A .257 Weatherby, not a .257 Roberts improved or a blown out 25-06 or any other practical, sensible boring solution.
I get this all the time when I mention converting my .375 to .378."Oh no it kicks too hard!" "Brass costs too much!" "Convert to .375 improved-way easier."
No I want a .378 Weatherby. Don't care how hard it kicks, how much powder it burns or what brass costs. That's what I want.
To OP-the .257 was designed with standard [30-06] actions in mind. Cake walk rechamber. Open bolt face, quick work on the feed rails, rechamber and done. Go for it, have fun, don't listen to these Studebaker driving old ladies.
Course maybe I am not the best to ask. I am also the only person I know that owns a .223WSSM