At my altitude, with my gun; 6.5-284, 140 VLD at 3015'/sec............MAXIMUM effective range on deer would be just a hair over 1000 yds. That is if you go off the minimums of 1000'lbs energy and at least 1800'/sec velocity on target, which is the most recent minimum velocity I read from Berger. In fact, he didn't advocate even fully relying on it at 1800.
I prefer to stay above those limits personally and would limit my shots under excellent conditions to 800 yds. A wind change or misjudge of only 1 mph can easily turn a 4" group into a 7" group at 800 yds. Therefore, 800 is my limit with this rifle for hunting purposes. At 800, I am still 2030'/sec and 1280 ft.lbs energy which gives just a little cushion if the wind does change speed by 1 or 2 mph.
Best of Luck, hope this helps.