Is there enough meat around the aperture to drill and tap for some sort of insert? then you could use it for both hunting and targets (in all lighting). If not, a better option might be a blank like pictured below, and then drill and tap that. if you don't like the inserts for the william's sights and such, you could make them from small, short bolts, just center punch them and drill them out to the right diameter for you (easier in a drill press, but the short length is helpful, as you won't notice if it was lightly off level and plumb when you drilled as much). A rubber o-ring will keep the aperture tight, without having to over-tighten it. Remember, aperture sights are best when they're mounted close to the eye, rather than further out like a notch.
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