Re: 25-06 versus 257 weatherby
If you do the 257 wby in a 26" barrel you are way faster than a 25-06. Loading manuals give you a good place to start and that is about it. Particularly with the wby calibers where they way underload them because some rifles do not have the wby freebore. You will need to open up the bolt face to do a magnum cartridge. I would suggest going to a 6.5-06 improved with the action you have. Way better bullets in 6.5 than 257 to hit harder at longer ranges.
Predictions are difficult, especially when they involve the future