Like Hoons so nice showed everyone the BDc is one great way to go and as Phx says using the BDC Circles and Spot On gives you exact numbers for the data you enter. I use it on all my hunting rifles and have never ben let down. Yes, I'm a bit bias, but believe me, I wouldn't be if it didn't work. Some guy's say they can't get past the "busy" reticle, but I've taken many ex-military guy's shooting who now own a NikonScope with BDC reticle.
Just in case some of you didn't know, there's a Promo. going on right now that includes ALL BDC reticle scopes. Who doesn't like to save some $ ?