I was about to do exactly what you but had another thought. I was using a very sharp needle if I can feel the the line but I can't, so I decided to clean it with a brass compound and here's the result: the ring is now totally goneThose cases are a hot mess! It looks like most of rings are in three areas of the case. I would cut a couple of those cases in half and see if there is wall thinning.
I will shoot factory some ammo and new brass reloads to further verify what the heck is going on here and will cut some of the ring-ec
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We just shot factory and new brass and no ring marks at all. I also checked them after the sonic cleaner and they were fine. However, the old brass that we also shoot have little marks on some of them. It was not as much as the last time. I think my friend did something wrong on his prep processing. Thanks.With it being four different rifles, think I would look at brass prep. Do they go into the cleaner with marks on them? If you can't feel a ridge with a pick and you can clean off marks it looks like some kind of tarnish issue or chemical reaction.