Magnumitis seems to be buzz word for compensation to practice and learn your rifle. If all you do prior is shoot whitetail under 100 yards, you're never going to be able to make a 400 yard shot with a plain duplex reticle.
If you get out and practice at various distance out to 1000 yards,you're going to learn your rifle. Pretty soon, that 400 yard shot will become a chip shot.
Practice, practice, practice....and know your ballistics.
