I do not think X-rays will show internal pitting, or at least not distinguish interior pitting from other things that will show up. Damascus barrels are comprised of strips of steel and iron, wound together and hammer welded together around a mandril. Inside the welds, are hard spots, soft spots, slag inclusions and actual small cavities or voids. Over time and exposure to the elements and stupidity in failure to clean properly, they become pitted, some more, some less. How deeply these pits run is only a guess, as they can actually work their way all the way through a barrel's breech, let alone the tube itself. One must be very careful about selecting (buying) and shooting a damascus barrel's gun. The 'proof' test is the only real test. If it blows out, it was a poor buy. Guns are not held to the shoulder when proofed.