I've heard you can determine straitness by the the reflections inside. Clearly, a low-angle view down the outside will tell you how well they're faired in the filing. I'd need a crystal ball to determine "concentricity" of bore channel (presumably meaning consistent wall thickness radially) without a w/t gauge and I doubt if I could look down a bore and tell you it's a consistent diameter all the way down. But I ain't Superman

jack