Another tool that is valuable. A good bore gauge. I recently bought a 16 gauge gun that looked good on the outside...barrels chimed with a nice ring. ...but just before the choke on the right barrel my bore gauge read.690 for about an inch. Wall thickness was .029. On close examination I could feel the bulge but it was very hard to see. The gun was returned. Oversize "mirror" bores make me worry also.....have to check them carefully. This true for fluid steel or Damascus. A bad barrel is a bad barrel.