I drop a 2 section of solid brass rod down the bore, hold the gun vertical and pull the trigger. If it has a good firing pin and spring the rod will jump noticeably in the bore. You can also determine how strong the spring is. If its just a wimpy jump the spring is probably too weak or firing pin too short. Great item to carry when looking at guns at gun shows, etc. If the fall of the hammer sounds normal but the rod doesnt jump then the firing pin has a problem.

John McCain is my war hero.