When you first get out to some long range targets you will most likely find that your drop sheet was maybe close, but not precisely on target.
This is where you refine your data.
Record the actual corrections needed, to hit accurately. Try to get some actual data points at at least a midrange distance, and a long range distance. I like to test at around 300, 600, 900, 1200 for actual fired data.
Then, when I get back home to the computer, I go into my ballistic program and tweak MV, and/or BC until the calcs line up well with my actual fired data. Once this is done, you will typically have good accurate correction data at any intermediate distances between your recorded data points.
Then get out there and shoot often at various distances and wind conditions. you may need to refine your data again, but you will be gaining experience with the wind and shooting from field expedient positions.
