If the Nikon comes with the mounts try them out and if they don't hold zero step up a grade or two . I suspect they will hold zero just fine . You also need to keep in mind you have an AR not a competition bolt gun . Not sure how much of a difference you will notice from $60 rings to $200 rings .
As of this date 8-18-14 at 6:42am I became a proud grandfather I guess I'm officially old