SawDoctor,
The feasibility of rechambering would depend a little on barrel contour. It might not be truly practical in a #1A with it's light barrel, but would be no problem in a 1B.
In my experience freebore doesn't affect accuracy if the freebore is "tight," meaning just enough to allow a .308" bullet. We have three Weatherby rifles in the house, chambered for the .240, .257 and .300 Weatherby Magnums, and all are VERY accurate. So it would depend mostly on the reamer your gunsmith uses.
