93r17 and Boyd's stock

About 2 months ago I bought a 93r17. Its accurate enough to hunt squirrels with. For Christmas my girlfriend bought me a stock from Boyd's. the varmint. I headed out to the range and found it to be extremely accurate at 25 yards so I moved out to 50 yards and found that it was hitting about 2 and a half inches high. Before it would be almost dead on. I'm trying to figure out why that is. I torqued it to 15 inch pounds and then went up to 20 because Boyd's recommends the stock torqued between 14 and 26 inch pounds. The difference happens when I was at either torques. Any information at all will be greatly appreciated thank you.

If you zero at fifty it will shoot low at 25, if you zero at 25 it will shoot high at 50. Using Hornady 17 grain, the difference should only be about .56 inches or so, even 20 grain should only be about .5 inches or so at these distances. If you didn't make any changes to the scope, maybe you have a scope issue?