A point I think worth considering is, if a shotgun tube has been welded and formed to show a correct finished pattern, wouldn't reforging to some smaller diameter distort the pattern.
Also, if the correct pattern is uncovered in the center of the material, to some extent the better rifled barrel makers might have intentionally welded them up differently than a shotgun tube to account for greater wall thickness and appearance.
Craig,
Reforging a tube would cause a small change to the damascus pattern, though not significant. It would only cause the pattern to be slightly smaller. It would be entirely possible to select a shotgun tube that had a pattern of a size that would look appropriate after reforging.
In Greener's comment about making damascus rifle tubes, he does also state that they were welded of thicker riband. Having thicker barrel walls on ball and bullet barrels would seem to be logical. Though for black powder use, thicker walls are not entirely necessary for containing pressure. With a barrel for a gun intended to fire very heavy loads, one would want thicker walls. But as with the barrels on the O/U pistol that Drew posted, they are fairly thin walled. There is a whole myriad of considerations for barrel wall thickness, including how the barrel will be breached and how it will be affixed in the gun stock. There is also some consideration for the thickness of the riband, to effect the creation of the damascus pattern. It's a deep subject and one for which I am not certain that I have all of the answers to; only some experience based speculations. It will require a rather lengthy dissertation to work through my hypothesis. In other words; it's gonna' take some 'slpaining. I think it would be better if I start another thread on the topic. Things are about to get busy in our house for the holiday. I'll try to compose some words and post in a few days.
Drew,
Just for clarification, moire' describes damascus that does not have a distinct created pattern?? Random swirls??
The barrels on the percussion pistols seem to me to be faux damascus. The direction of the layers in the pattern seem illogical. Though if faux, they were thoughtful enough to etch in lines for the riband edge welds.
The Valentin barrels look like genuine damascus. Maybe a conglomeration of scrap metal pieces.
The pattern in the knife blade, I would call a lazy ladder pattern. Low layer count and wide spacing on the ladders. Below is a bowie that I recently made. The blade is a 330 layer ladder pattern.
