I've seen barrels that were over stressed and looking down the bore the rings were easily recognized.
I've seen "stress" rings when it was nothing more them bad lighting.
Then there are times that I don't know what the heck I'm looking at.
Does looking down the bore using a 12guage shell with the primer cap removed at the breech end and a 20 gauge with primer removed at the muzzle end give an accurate indication of stress rings?