Thats a great starting point, thanks. I can see a twisting machine too but generally feel like the hand welding of the spiral welds is likely the best way, but for this process only. Generating many miles of thin bars in iron is a chore without rolling. Especially since uniformity is paramount, even the best hammering isnt completely uniform. If you add the dissimilar metals, the tendency of iron to delaminate and the rapid cooling of long thin sections, I again wonder if rolling was common as a means of generating the raw material for the barrel welders.
Here is a link, lots about rolling mills but no mention of damascus.
modern damascus makers use rolling mills and the technology was available during the breachloading shotgun era.
https://www.ispatguru.com/historical...ts%20thickness.