I inherited back my own ruger 10/22 recently (step dad hogged it for 20 years) and I had a Nikon monarch on the shelf. So I went to Wally world and got a 2 piece weaver mount and rings. I mounted it up and I am shooting 6 inches low at only 15m. The iron sights are dead on at this range. I maxed out elevation and I'm still 6 low. I tried swapping the rings. What else should I try? Lapping the rings?