By the looks of the barrel I would say you have a Damascus twist steel barrel and I think the reference to fine twist on the receiver is proving its a damascus barrel. The reference to nitro powders normally, is smoke less powder, but I doubt that it means modern day powder. Back in that era they had a powder made by Alcan that was smokeless, but more like black powder pressures and burn rates. It was called Ballsite.
If you have time to do it twice, then you have time to do it once right and put your name on it