RE: 3-9 or 2-7 or 1.5-6 power scope for muzzle loader?
Though I've used all 3 that you mention, I only have 3-9s now. Some 40mm some 50mm. 90% of my shots are about 30-40 yards as well. I leave it on about 4.5 and crank it up if I need to. I don't think you could go wrong with any of them, it's just a matter of personal prefence.