Re: 257WBY 115gr BT or 115gr Berger's???
Around four years ago my friends and I built five 257 weatherby chambered rifles. We asked Dave Kiff to make us a reamer for the 115 VLD. We specified less freebore than Weatherby uses. There still is some jump to rifling. I use .070" as do some of the other shooters, one guy uses .100". So the 115 VLD WILL shoot without being into the lands.
As for killing, oh boy what a bullet! I have seen my rifle kill three coues wt for me and one more when my friend used it last year. The ranges were 525, 400, 385, and 350 yds. Two dropped in their tracks, the other two staggered around and fell within 15-20 seconds. Entrance holes were small but within a few inches they became much larger. This year's deer is fresh in my mind. 385 yds quartering towards me, entrance just behind shoulder exiting ribs on far side. The edge of the shoulder had a small hole, the entrance side ribs had a 3" diameter hole and the exit was just a bit larger than bulllet diameter. The lungs were total mush.
One of the guys uses his in Co. He has killed three elk and three mule deer. He swears by this bullet for elk! He says two elk instantly dropped to the lung shot the other ran a bit then dropped. Same results for his mule deer, very fast kills.
This 115 VLD has a high BC and bucks crosswinds very well. The bearing surface is minimal something the 115 Nos Bt is lacking. If you can get the VLD to shoot use it with confidence.