I mounted a Bushnell Elite 4200 on my Ruger 77 and just cant get it zerod. It shoots 3 inches low at 25yds no matter how much i adjust elevation. I is about 1.5 inches low at 50. I have adjusted it all the way out and it never changes. I am using the medium ruger rings that came with the rifle (chambered in 357). Is this a ring alignment, or a scope or operator problem? Suggestions?