The best thing to do is to just go some place you can shoot at that range and practice becoming proficient from 300 mtrs, and work your way up and see what you can do and learn the specifics on what the weather conditions do to the type of round you are shooting and go for it. Shooting long range with any weapon comes natural to some and alot of us have to practice and keep it up to stay accurate at long ranges.
If you find you can get hits at long range damn sure have a witness to back it up, I've made some lucky long range hits with my issue M4 but kept my mouth shut cuz no one was there to back up my claim!