Joined
·
833 Posts
Seems pretty simple to me. Look at the rear of the ejection port. The block is angled so that ejecting brass hits it and heads somewhat forward and down and also imparts a "flip" to the brass which would cause the case mouth to strike the receiver. You can also see on the bottom of the ejction port itself, there is similar wear, probably caused by the same thing. Ejecting brass does all sorts of weird things depending on what it hits and the slight variations in ejection speed