Thanks doc after gun maker puts barrels exactly on face I will just shoot sub 5000 psi loads in it. I have a set of 16ga x28ga tubes if I get nervous. Man they ring as good as any barrels I have tried! I found 3 sets of Bernard barrels(on internet) 2 were pin fires,with 17.2 mm marks and they ranged from .675- .680 not counting these. Hopefully they started life around .675, but measurements look safe enough for black powder pressure levels.