Only my 2 cents, but I would pass on the .257 Mag. It is a screamer and a game getter, but still a .25 bullet. More recoil and more noise, but still not any bigger, just faster. If you buy factory ammo, it is approx. $35/2o rounds. I would definitely buy a 25-06 first and prefer a .257 Roberts.
By the way, I have hunted with each. I now have the .257 Roberts as my "go to" .25 bore.
I love the Vanguards and the Howa 1500's. But not in the Weatherby calibers.
OMHO
pepaw