The blacksmith at Rodmell forge told me that when steel was in short supply due to WW2 the shepherds would bring him old shotgun barrels to be made into the Sussex leg crook. When he tried to reduce the diameter on Damascus barrels they came unwound. It was never actually welded.
Similarly, if you wind a Damascus barrel then rifle it, you are cutting across the grain of the Damascus and the rifling has no strength. A rifled Damascus barre starts with a tape wound core.
I have one of the original Liege Damascus shotgun barrel blanks Peter Dyson was selling off. It has a beautiful loopy pattern. Wonder if he has any left.