You need to sight in you rifle in "ideal conditions" at a rage were you are confidant. and figure out you're bullets trajectory so you know how much it drops at ranges past you're zero. A mirage will through you off every time until you figure it out. If you're going to keep talking long shots you might want to put out some wind flags at different ranges so you can see what the wind is doing and more importantly so you can see what angle the mirage is "moving." Then go practice and keep notes of how far left, right or high you aim and where you hit. Practice.