These will get you started, you can download apps to your I phone for bullet drop also. I'm pretty sure the BDC reticle will only work correctly at the power setting that it's designed for on a second focal plane scope, a first focal plane scope works at any power setting. http://www.federalpremium.com/resources/ballistics_application.aspx http://ballisticscalculator.winchester.com/ http://www.biggameinfo.com/index.aspx?page=%2fbalcalc.ascx http://www.foxnews.com/story/0,2933,481004,00.html