Re: Vortex Viper 4-12x40
I can't help you with that exact scope, but I do have two other Vipers (2-7x32 and 6.5-20x44), and they're definitely solid, quality pieces. I wouldn't hesitate to put one on a muzzleloader. The glass is pretty clear, and the construction is heavy duty. Worst case, the warranty will take care of you if it doesn't hold up (though I don't see that happening).