I've started to play around with the Barnes TSX 180gr bullets for my .300 WSM, and they are wicked accurate. I chose them for general use on elk and mulies, and I can't wait to see how they perform on either one (heck, I can't wait just to SEE a live elk, let alone harvest one!) I like the idea of virtually guaranteed pass through penetration combined with excellent expansion. I've never heard anything bad about them, and the accuracy potential over the conventional X-bullet is turning out to be very true. I'm sure a TSX would work very well in your .257. I might even step down a notch and use maybe the second heaviest bullet for a little more velocity since the TSX's are supposed to penetrate so well.

Mike