Linseed is a classic stock treatment. But it stays tacky for a long time, depending on many factors, and never really becomes a solid like modern polymer finishes or the like. At least with Tung oil it does seem to dry faster for me and does not need re-apps. like the military wants on their guns with linseed. Frankly if the original finish is intact on your Mauser, maybe consider cleaning it to get off any surface dirt or crud with something like Formbys furniture cleaner which is fairly mild. Then maybe wax it. Good gunstock wax will work and improve the appearance of many old finishes. Otherwise get a German or Russian(?) armorers manual or something and go for perfect authenticity. Lot of the captures I have seen though, had that uckly shiny shellac type finish instead of what the Germans used. Now that would be worth stripping and redoing.
Your gun is like your nose, it is just wrong for someone else to pick it for you!