I posted this on the barrel board, but didn't get much help. Some years ago I had the barrel on my '73 Winchester relined by Redman. He advertised .428 groove diameter. It turned out to be .431. A .431 bullet seated in any of the readily available cases chambers too tightly for my comfort in a '73. What I would like to do is open just the neck of the chamber a few thou. I thought of turning a short cylinder of brass that would screw onto a cleaning rod, then coating it with lapping compound or emery cloth and pulling it into the chamber from the muzzle using a cleaning rod, and spinning it with a hand drill. Any suggestions are welcome. I'd prefer not to take the barrel off.