Thanks Edgar.

I've seen dye-penetrant testing done, and have heard of mag particle, x-ray, etc. I wonder aloud if any of these be done to verify a defect on the INSIDE surface of a shotgun barrel ? Then, would a deep scratch & a small crack look alike to some of these methods ? Would localized, linear pits/corrosion look like a crack ? I did have a friend with a scope video the bores (both of them, before the honing), and although it's not a perfectly sharp video, you can definitely see this "defect." It's obvious (as were the many pits in these bores, a lot of which are gone now, due to the honing).

There are many such testing companies in the area - I should look into it.

Thanks !

PT (Penetrant Testing) will detect and clearly show a crack which is thru-wall, but if it doesn't extend to the outside, may not be the most suitable.
Shear wave UT(Ultrasonic Testing) will show the crack whether thru wall or not but operator experience is more critical.
RT (Radiographic Testing) is more expensive, but whether single wall (film on one side of barrel wall, source on the other, is practical is up to the individual lab. Double wall will still show the defect, and two shots at oblique angles will give it definition.
Trust me when I tell you, the Navy wouldn't send sailors down in submarines if NDT wasn't a proven discipline.

I believe you.

Thanks again !

Edgar, are you a recovering Bubblehead?

Casey