I use Nikon Pro Staff scopes on three muzzleloaders. Two of the rifles shoot between a 450 and a 500 grain conical bullets and lets just say recoil can get hairy. My Nikon Pro Staff scopes have never budged off dead on. I also have them mounted on Warne Quick Release rings and take them off and put them back on, still with no loss of accuracy.
Their clarity is excellent. The glass is amazing for the cost of the scope. The focus is fast and so is their light gathering ability. When I took my muzzleloader in to the gun shop to purchase and professionally mount a scope, I asked the owner what scope he recommended. He stood there smiling and said, I could sell you a big dollar scope and you'd like it. But the one I recommend is the Nikon Pro Staff. As he explained, they have a Nikon Warranty, Nikon Quality, Nikon Glass, and I sell a lot of them but they never come back. Not for repairs or for trade in. He then said, that tells me that once people get them, they hold on to them.
Also, I am not a big fan of a BDC. I have a couple of them on rifles. And they do work well. Another favorite scope is a Nikon Omega 3-9x40mm. Again, great eye relief, excellent glass, just an exceptional scope.
Another great scope is a Bushnell 3200 Elite. I have that on a muzzleloader and find it an exceptional scope. Now granted these are not Leupold high dollar scopes, or some of the other brands. But for the kind of hunting I do they work perfect and have never fogged up or let me down.