Drew,
That last picture is very telling of how the laminates were laid up in the billet. See the small lines in the scarf weld. That is the stacking order of the laminates that made up the billet. That would have been what the end of the billet would have looked like. Distortions to the layers from forging would displace the laminates irregularly. So when the barrel surface was finished. The on edge pieces would create the straight lines in the pattern. The pieces that were laid flat (parallel) to the surface of the barrel create the broader lines.
It's very possible that the Damascus Twist, London, or Baker "Best London Damascus Twist" was made this way. Looks very similar.
