Well...a bit more information from you would help you get a useful answer.
Have you ever shot the rifle before? With this load?
If so, what were the results you got from that session? Sure, anyone can plug in numbers and hope for the best, but without a little bit of verification that your rifle is indeed shooting as expected...
What bullet are you using? Berger, Lapua, Sierra Nosler, Cutting Edge, other? What is the BC?
What program or calculations did you use to get your numbers?
Is that muzzle velocity verified by a Chronograph of some sort? At muzzle or 10 feet away?
What is your zero range? 100?
What are your atmospheric conditions where you shoot? Altitude?
Just making guesses at some of the answers to the above question and plugging them into Ballistic, I came up with 17.9 MOA at 800. See what I mean?
Garbage in, garbage out. Sure, you can start at 17.2 and dial in if you have no better info, as long as you have a good spotter or can spot your misses yourself, but...