its not really that diffacult, I got really serious about it in 1996, have taken I think 56 deer beyond 400, of those 20 couple were beyond 700 yards, a dozen beyond 800, a handful beyond 1000, and a couple beyond 1200 yards, but you need an accurate rifle paired with a shooting system to get it done.
the rifle puts the bullet where it needs to go, you and the system steers it. here is what I carry to the field to make hits possible at up to 3/4's mile

RR