From just about everything I have read on the subject, final barrel striking and polishing is virtually always done after the barrels are joined and the ribs installed. As such, the barrels are naturally going to be thicker between the ribs. Any subsequent refinishing over time that involves striking and polishing after dent removal is going to further thin them. I have no way of proving it, but I have heard of more than a few guns from quality American gun makers that had exceedingly thin areas, and allegedly had never been honed or otherwise refinished. I'd be interested in hearing what kind of measurements you get in your 20 ga. Flues Lloyd.
