Todd, the biggest variable is the wind. What it's doing where you are is usually NOT what it's doing down range. Wind can move bullets up/down/left/right and that can be all in the same shot! I've watched bullets move right, then left, then back right to impact the target. In long range shooting, when behind the shooter if you have good optics, you can actually watch the bullet "trace" as it disturbs the air when it goes down range.