John: I believe (hope) that radiography is the best non-destructive means to assess what is happening within the barrel wall; inclusions, voids, weld failures, non-weld cracks. Just as with an MRI of any body part, interpretation of course requires an expert and experienced human eye. No one at TEAM has x-rayed Damascus barrels, but they have lots of experience in industrial applications of radiography.
I would very much suggest that a 'linear defect' seen on radiography is real, and really a crack, and really an indication that the barrel is unusable. Of course, sectioning the barrel for photomicrographs would confirm the diagnosis if you would like to donate the barrel to science
Unfortunately, the two barrels I've had x-rayed so far show only what is very likely to be pits
on (not within) the bore wall; defects that are not linear and can be correlated to the findings on visual exam of the bore
Negative image - defects grey/black. The white stuff is felt to be porosity in the solder
I'm meeting with the techs at TEAM again in the am and should have more images thereafter, and another barrel is arriving today with an apparent crack visible on the outside of one barrel. SO I will have at least three more barrels to x-ray for the data base (total of 5).
One thing clearly shown is that the mythology that pattern welded barrel walls are 'a mass of welds, voids, inclusions, slag, etc.' is wrong. We'll have more evidence when the photomicrographs are done on the barrel blow out analysis.