I have a tip that may work for you. I recently needed to turn a standard synthetic hunting stock into a stock that would accept a varmint contour barrel. I did this by putting my turkey fryer pot full of water on the heat until it started boiling. Then I placed the fore end of the stock in the pot and let it boil for about 5 minutes. I then forced a large wooden broom handle about 1" in diameter into the length of the barrel channel from where the tang sits out the front of the stock and wrapped it with duct tape to hold it until it cooled. When I was done I had a perfectly straight wide barrel channel without removing any material. If you didn't know I did it you would think it came from the factory that way. I went from a 30-06 pencil barrel 110 long action to a model 10BA .308 barrel and it now fits perfectly with no contact.
Good luck