Altough expensive probably a best bet.. I was going to suggest holding the stones or cutters in a Pin Vice and attempting to do the work by hand..............Oooops! If you want to try the power route... conside the Cratex? Grinding and polishing tools they are made out of Heavy Duty polishing/grinding compounds and are consumable? I have made my own Big Bore from scratch. I used a ball end stone but the hole was much bigger(making the job easier) and was also easier to see from the breech. Good luck!! G