I don't know anything compared to these guys, but I'm interested in this kind of thing myself. First thing that comes to mind is round barrel channel -- can't see a reason to do it any other way. Bottom of barrel itself, as well. PB inside also -- even in pictures you can see the drill used a lot of times. I also think the file marks in the BP in line with the toe molding were not style statements originally. Pits in castings weren't always meticulously filled, either, as far as I can tell.
Alternately, as was said, if you do anything long enough, you will get better and faster, so I don't think sloppy inletting or other obvious shortcuts were common originally, though the wood shrinkage and other factors may make people thing they were, but early rifles probably weren't held to the same standard of perfection as our showpieces.