12-20-2013, 07:09 PM
Yeah, I just checked an Aero that I am using for another forum member's upper, and it is almost dead-on. Spin the upper on the tool with a bright light in the background and look carefully at the edges. You can see then if it is out or not, or just use Dykem fluid on the receiver face, let it dry, then skim the face with the tool in a drill and see what happens.