Quote Originally Posted by johnnyrem View Post
What I see is an extracted round that has failed to clear the ejection port.

I would quantify how different these are from your regular ammo by running them over a chronograph. If there is no difference in velocity I would look at dimensionality of the cases near the rim. If there is a noticeable difference in velocity I would post that here and go down that rabbit hole for awhile.

The fact everything else runs right says ammo rather than the gun. You just have to find out what it is about the ammo.

Do you handload? Would be helpful if you did.
+1 This is all exactly what I was going to suggest, but you beat me to it.