Remember though that English and German guns were stocked in English Walnut or Juglans Regia, while American Black Walnut or Juglans Nigra is a completely different wood, both in appearance and workability. I love working with European or English walnut, it carves beautifully, finishes easily and is nice and hard. Personally, I am not that big a fan of black walnut, while it cuts and sands easily, it can be brittle and liable to split and must be filled and sealed before finishing or it looks atrocious. As Mike said though, it is appropriate wood for Appalachian style guns. If you look through Shumway's RCA, you will occasionally see a rifle stocked in walnut, might check those out as an idea for a build.