Re: long range targets
Exactly what Huckelberry said. I did not pay real close attention to these aspects until I shot a proper fitting rifle and scope. It is worth spenging the time and money to really fit that rifle to you. Is amazing how much that alone helps consistency and accuracy.
As to the original question. What I do with centerfire is set up a 25, 50 and 100 yard target. Shoot the 25, get close, shoot teh 50, get close, shoot the 100 for accuracy and establish THIS as my zero with THIS ammo. From here I us JBM Ballstics and build my test DOPE, hit the real world and test DOPE and make adjustments. I find that JBM is pretty dang close, close enough that I only need to make minor adjustments.
This is a little more than you asked for, just trying to head your next question off at the pass!