I'm looking for a little advice here I hope someone can help. I was at cabelas this weekend and picked up a tang safety ruger 77 in 6mm with a 6.5X20X40 leupold Vari X III. The gun is in great condition and the scope is too. When I got the gun home and looked through the scope more extensively a darker circle appears around the outside edge as I turn the power from 6.5 to 20, as the magnification increases so does the darker circle. The circle extends about a 1/4 of the way in from outside edge when the power is turned up to 20. This doesn't seem normal to me but I have never had a vari X III. I'm just looking to see if this is something that is normal with these scopes or if I should go ahead and send it back to leupold. Thanks for any help you can give.