Well If anyone care several years back I just used the Weatherby 115 BT ammo. I took one antelope doe at 258yrs and the bullet logged in the off side shoulder under the hide fully opened. 2 days later I shot another at 398 and had complete pass through with about a quarter size hole on the exit. Since then I sold the weatherby for a 6.5x284 Norma. I was surprised when the new weatherby came out with the 300 case necked down to a 6.5. I think the 257 necked up to a 6.5 would of been more practical. But that would of been I think almost the same as a 264 win mag or just slightly over.