that is not a rifle I would dump the money into myself, they shoot good as many makers barrels in stock form. if you are doing it to practice your smithing' skills, then more power to ya. if it were me and I HAD to rebarrel a 300wsm, I would go to 6mm, 6.5mm, or 416.....something with more to offer in the way of change then the diff between 270 and 308......but to each his own.
ENJOY!