On both my 11.5 and 14.5 SBR lowers, I am absolutely unable to utilize any other mil-spec upper receiver because of the pivot pin fitment. None of my Colts or any of the other Aero/Square Forge uppers I have will work. They are fairly tight on the KAC uppers as well. There is a very noticeable cant (about .010-.015") in the pin as it can be tilted up to go straight into the opposite bore without any effort at all, but still binds up very badly in the front lug of the upper on anything other than Knight's Armament. It's almost like the pin is out of spec. Has anyone encountered this?