Re: 300 winn mag to 257 stw
I've got a Savage long action Tactical that I had rechambered from 7mm Rem Mag to 7mm STW. The smith ground back the bolt stop to allow the bolt to travel a little farther back and spliced two internal mag boxes together to make a new mag. That plus a new follower made a nice 7 STW. The action is plenty long enough for an STW.
Leftys are the only ones in their right minds!
(and I ain't talkin' politics!)
NRA Life Member