Hi Dennis,
The first 2 rifles I made were stained with nitric acid and then potassium permanganate. The brownish color from the K perm was good initially but it changed over over time. The reddish undertone from the nitric acid never changed color. With respect to maple, I really don't understand why anyone would not simply use ferric nitrate and water. In my opinion, everything else is just a waste of time and effort except if you want to supplement the ferric nitrate stain with something like aniline dyes.
dave