A friend of mine has a older style muzzleloader like you describe and we put a scope on with epoxy,it never broke off or anything.We used a mount that was for a 30 06 rifle.It had a flat bottom so it worked well.We just mixed up the epoxy and put the base on and lined it up straight,let it set good and mount your scope.I can' t recall the name of the epoxy but weldbond makes an epoxy that would work great.Hope this helps.