If you are going to do it yourself, you might want to invest in a Brownell's crown facing cutter. I mount mine in an old fashioned bit brace. This gives enough flex that the pilot can do its work, but you are not likely to apply enough force to introduce a bias and get a crooked crown. Using an electric drill, you can easily get a biased cut. I use the piloted bit without tightening down the set screw, so that the cutter can rotate around the pilot stem. I hate the idea of cuttings getting in there and being ground against the rifling near the muzzle when they get embedded in the brass pilot. I also get the barrel as level (horizontal) as possible and keep the cutter in line with the axis of the barrel. Clean often - including anything that might get inside the muzzle and go easy. If you have a good quality sharp cutter, you will not have to apply too much force. PTG (Midway USA) also makes good crown cutters. They have a sleeve over the pilot that remains stationary in the barrel. Pilots for unusual calibers are hard to come by though. It is VERY important to get a good, square and clean cut to begin with, though. Works for me anyway. Hope this helps!
