I have cut off many barrels over the years. And, like you, was very concerned the first time. I had the first one turned off on a lathe, by an old gunsmith, and hand crowned. Heck, it cost me more than the barrel. The next time I needed a barrel shortened I asked one of the best muzzleloader shooters in our area, that builds all his own guns, if he would do it for me. He said sure, no problem, drop by any time. I stopped by one day, and before I realized what he was doing, he stuck the barrel in the clamp on his cutoff wheel, and the sparks flew. I was still gasping for breath, when he snatched up round stone for his electric drill, and crowned it for me. He handed me a piece of Emory cloth, and told me to wrap it around my thumb and polish the crown. I was sick at my stomach, but was determined to shoot the gun before reading him the riot act. Sun of a gun, it's the best shooter I own. The most important part to remember is cut it square,don't overdo the crown, and polish it up good and slick.
Hungry Horse