Quote Originally Posted by Willoughby View Post
I ask someone who was using one -& he said it learns what ever you sight in with
obviously - all you need is money to buy one -not ballistic information
No, they don't "learn"; they don't possess artificial intelligence. And Yes, you do need ballistic information if you go with a custom turret dial. The Leupold CDS requires you provide altitude/average yearly temperature where you shoot. Then, you'll need bullet weight, coeffecient of drag, barrel length and velocity. Now, the generic BDC reticles as helotaxi mentioned work around a fairly loose set of known/assumed parameters.

Neither method is suitable for more than hunting and should be verified on POI at the reticle marks. Stuff like wind/angle/mirage cannot be factored in.