Once you screw with it enough its not a Nelson Lewis anymore. UNLESS its PROPERLY restored.
Nor do i trust old barrels, even barrels on breechloaders of the 1880s show some frightening flaws and inclusions.
If this rifle is in this poor a shape I see little point in it being made into a shooter.
I have a 42 +- cal W.H. Moore Rochester marked rifle that is a shooter. A friend was shooting it and I think I have the loading notes and other things needed to shoot it in the hard case it came in, except its been shortened about 3-4" at the breech, the patent breechplug removed and a drum and nipple (with a copper washer to take up slack at the barrel) installed years ago sometime between maybe 1870 and ? Drum is old. A hook is filed on the "new" breech plug to fit the standing breech and its been arc welded at some time to build it up to fit better. Lock plate has been filed and polished around the drum to remove the sharp edge where the patent breech fit.
I got the rifle in a trade some years ago with accessories, it was a picket rifle but there is no starter or original picket stuff. So if I wanted to shoot pickets I would have to make a starter and a swage, then I would have to find or make a patent breechplug and set the barrel forward to avoid removing the "W.H. Moore" which is now close to the breech so I would have to cut another groove in the barrel and bridge it for the key like the original and the second one are done.
Its not worth it. I would have more time it in that it would be worth.
Very nice old rifle but I will never shoot it.
Dan