Hand-loaded .257Wby. ammo will be around 3.3" in length. Is your existing magazine-box long enough?
Of course, the bolt-face will need to be opened-up for the larger rim diameter.
I'm not an expert on changing calibers, but have you considered the 25-06 cartridge? It's slightly slower than the Wby., but the critters will not know the difference. And you can still use all those '06 cases.
The magazine will take 200grn Factory loads. I have also loaded this 30-06 up to the max recommended COL of 3.34”. I do not have the rifle in front of me right now, but am going under the assumption that the mag will be long enough. I will be getting out the calipers when I get home. Also I will get my hands on a few rounds in 257WBY from my Smith, and seeing how they fit. The LSA action is smooth, and the current 30-06 shoots the 165grn at about .4 MOA. I just have too many 30-06 rifles, so it is time to get some other cartridges going on the actions I am not using. I have considered the 25-06, but as you may be able to tell I am a little partial to Weatherby. gun)
Sorry I have been out of country for a while. The answer is no. I do not sell guns, I only buy them. The action, and mag are long enough, and there is a 26" Ron smith barrel on its way. gun)Good luck to anyone looking for one of these actions, in my humble opinion they are very smooth, and reliable.