I have a .17 HMR, Remington 597 w/ a Tasco 6x24 scope mounted on it. I have shot it before and was sighted in at 50 yds, w/ a nice tight group. I have not used this gun for a while, and took it out to the range to plink a bit. I was hitting 2' low and to the right about 8". I have no idea what happened. I tried turning the adjustment knob up, but it went all the way, and I am still over a foot low. What happened? It was in my gun safe, so it did not get banged or dropped. I am shooting the .17 HMR by Hornady. This is driving me nuts. Any suggestions? Should I try a shim or 2?