I recently purchased some once fired 5.56 brass. I deprimed/resized them, tumbled in stainless media, trimmed, deburred, swedged primer pockets, etc. Needless to say after all this effort I'd like to be able to use them. After they were ready to start reloading I noticed a ridge around the neck right where it meets the shoulder. It's very narrow but it still concerns me a little. I tried resizing it again but the ridge is still there. The empty case chambers fine but is difficult to extract. Am I doing something wrong or is this a known problem with 5.56? Could it have been from the chamber of the gun they were fired from? Should I load some of them and see if they will run through my AR? I have been reloading for several years and I've loaded quite a bit of .223 but I've never noticed this with any brass before. Any help would be appreciated.