Ringing is only one test, but I think it's a worthy one. I have seen gunsmiths do it. Foolproof? Nope. I've found some loose ribs just by pushing down with my thumb and detecting movement. The water test . . . might work OK after you've paid for the gun, but most dealers probably aren't going to haul out a tub of hot water for you to use. As long as you're working with a dealer that has a good return policy, however, might be interesting to try at home.