If I'm not mistaken, scopes are illegal on muzzleloaders in Colorado, at least during the muzzleloader season. They might be legal during the CF rifle seasons, but I'd check before you hunt with it. Otherwise, on a sidelock style rifle like the Hawken, I'd probably go with an aperature (peep) sight. Much more accurate and easier to use than post and notch style open sights. Just get an aperature that is bit enough to see through in lowlight and you'll be good to go.

Oh, and about powder types...do NOT use any type of smokeless powder in that gun. Use black powder or powders designed to be direct substitutes for black powder only (i.e. Pyrodex, Triple Seven, Black Max, etc...).

Mike