Kitch,
If you're still reading, check out the 6mm BR. Very efficient and will handle multiple, long shot strings without worry. Barrel should last 3-4 thousand rounds, or more.
If you just want a 257 Weatherby, go for it. It's a fun round and a real terror in the field, but like others have mentioned, it's not a round you want shoot multiple shots with from the bench. Also, to get the most out of it, go with heavier bullets. Preferably the 115 BST or Berger VLD. Lots of people swear by the 100 TTSX, but as Boxer illustrated, it's a ping pong ball and limits the bad azzness of the round. The 115 BST/VLD really let's you get the most out of the 257.
As for Weatherby Mark V rifles, I've always had great luck with mine. Accurate(MOA or better)right out of the box. Quality and reliability have been excellent as well, but then again I don't subject them to the extreme conditions as some here do. YMMV.
