Interesting question Aaron.
Descriptions of the tube making process from the early 1800s did not mention machine welding until this, toward the end of the damascus production era
The Hardware Reporter, May 9,
1913
https://books.google.com/books?id=15s7AQAAMAAJ&pg
“Process of Making a Good Shotgun - Barrel Depends Upon Materials Used and Method of Forming lt - Steel and Iron Combined.”
Two of these ribbons (rods) are required to form a single barrel, the one for the breech being somewhat thicker than the one for the muzzle. These ribbons are twisted into a spiral, this twisting being done cold unless very heavy barrels are desired.
The metal coils are next heated, a steel mandrel is inserted and the coil is welded by hammering. The two coils are next welded together, the breech section being about six inches long. Then comes more hammering until the metal is cold, and the barrel, is complete except for the finishing.
There are shops in Belgium where the method just described is followed, but in which
machines are utilized for twisting and hammering and where no steel whatever is used, the Damascus effect being attained by using two grades of iron. Such barrels are naturally more apt to contain flaws than a handworked product, and an all iron barrel is not sufficiently strong to withstand safely the explosion of the powders now generally used.
The 1891 Birmingham Proof House Test report listed many of the damascus barrels as "machine forged" but there was no explanation of what that meant
https://docs.google.com/document/d/1...hfDxmrNAU/edit
More here
https://docs.google.com/document/d/1...O8Fnk7kTQ/edit