Yeah, I looked at it from every possible angle and used those goofy "star chamber cleaning swabs" and everything and didn't notice anything abnormal save for what appears to be a visible female thread from the receiver extension, I've never seen this before in any barrel but I don't know if it is indicative of anything.
I wish I had a way to measure the gap between the extension lugs and the barrel face and compare it to known good barrels but my calipers don't fit in any of my assembled uppers and I'm not trying to dissemble any known good working stuff.
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