I had some .357 158 gr that were ostensibly "new", purchased from a gun show in 1990-ish. I took out a few to shoot (getting to the bottom of the barrel) and shot 46. 23 looked like this, scarring the cylinder of my Performance Center 627. Needless to say, I'm not a happy camper. Theory 1: The brass is old and brittle. Theory 2: They were reloads, and, hot. (No primer problems, though.) Theory 3: A combination of theory 1 and 2. Just for grins, I used a plug gauge and checked all my cylinders, they are fine. Any other theories? I have hundreds of these, and, now I'm afraid to shoot any of them in any of my firearms.