I get what you say but I’ve talk to two friends that own RimX that have more round count than me and dry fire and they don’t have any marks. Got the pics of their breech. Something doesn’t add up.Mine has the same marks. All the RimX's I have seen have the same marks. My TL3's have the same as well. I think it's just the floating bolt head. The clearance between the bolt nose and breech face is miniscule on a RimX and the bolt head floats so...it is what it is