Just to follow up on my post about the inconsistent ejection and strange wear in my XCR. I have spoken to Terra at RobArm and she has told me that yes, they have seen the strange wear marks before. They believe that they may be caused by a small blemish in the deburring of the rails. Terra had me send the upper (and internals) back to them for analysis, and they will be replacing the upper at no cost to me. Top notch customer support!
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