Anyone have any experience with Nikon buckmaster scopes? I have one on a Weatherby Vanguard 7mm rem mag with a walnut stock. I have Nikon Monarch on my savage 210f 12 gauge and had no trouble sighting it in. It's dead on for years. With the 7mm it is constantly changing. Is that too much rifle for the scope? I can't believe it's not something to do with the scope.