buy a set of traditions muzzleloader sights for a round barrel and then jb weld them right on there(if you take off the vent rib). I made a slug barrel for 70 bucks this way, bought an old modified barrel, cut it down to 19" and then jb the sights on an voila! Held 4-5" groups at 100 with them irons on it. And you can drill and tap a mossy receiver no problem. Go to your nearest "gun stuff" store and buy a cheap one piece base and get the correct drill/tap set for the screws that come with the base(usually 6-24 or maybe 8-24). Make sure you disassemble that action completely first. Be careful on the tap operation since the receiver is aluminum.