I've noticed a consistent small horizontal dance on my spent casings from my Glock 20. Anybody out there have an idea as to what this might be?
I was going to say, "It is not possible for the barrel to come back and contact the cartridge there." But it might under a couple circumstances while retraction of the spent case I suppose under some unforseen reasons the upper edge of the chamber could, so look for:Looks like as the slide is coming back the bottom of the barrel it is making contact with the shell in the magazine. This is probably causing your dent. As to why, I have no idea. I would suggest you take it to a gun smith.