Bill,
Being an engineer, I decided to take the high tech approach when faced with the same challenge, so I did the following to widen the barrel chanel on my Finnfire's stock:
I first ran a couple of strips of masking tape along each side of the barrel channel to protect against scratches. Then, I placed a folded towel between the jaws of my vise and the stock and tightened the vise around the stock just enough to get a tight grip on it. Then - this is the high tech part - I got some 80 grit sandpaper and cut 3" by 4" squares of the stuff.
I took the dowel off the toilet plunger, you know, the implement used to unplug toilets, and wrapped a square of sandpaper around it. I then worked the sandpaper-wrapped dowel carefuly back and forth along the barrel channel until I could slide a folded dollar bill between the stock and the new barrel, with the action screws tight. Leaving the tape in place along the sides of the barrel channel, I cleaned the barrel channel with alcohol until no sawdust was left and let it dry overnight.
Next morning, I applied a coat of Birchwood-Casey stock sealer to the barrel channel and let it dry for a couple of hours. I then applied another coat and let the stock dry overnight. I removed the masking tape the following day and the tock was ready. The only drawback is that I can no longer blame the rifle... :wink: