They are great tools, but like one's unmentionables should only be used with due discretion. As far as gun work, I've only used mine to polish the feed ramps on semi-autos using nothing more abrasive than Flitz or Simichrome. Fantastic results.
I've watched the best Smith & Wesson mechanic I've ever known use his to contour, smooth, and polish a trigger for double action shooting. When he was done, the trigger looked like it was chrome plated, was as slick as snot on a doorknob, and a great enhancement for double action shooting. Since then he has done several others for me. He's retired now, but I've got one more that I'm trying to get him to do his Dremel magic on.
Perhaps the OP had a bad experience first time out with his. Due discretion!