My Barnes manual says ...1.49" high at 100yds; 0 at 200yds; -6.58"at 300yds; -18.93"at 400yds. Soo...
dead on at 300yds would be 8.07" high at 100yds. I would sight in 4" high at 100yds, that would put you 4" low at 300yds. You could hold dead on at any range out to 300yds. I have to really question the caliber of guide you have if he wants you shooting 500yds at elk[>:].