Shot this Texas Whitetail at 603 yards with my 6.5-284 loaded with 140 grain Berger VLD at 2940 fps. The deer dropped like the rug was pulled from under it. The estimated energy left according to my ballistic program was around 1,300 ft/lb. Depending on the elevation, the cartridge is an honest 800 yards killer for deer size games.
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.
My favorite load for my 6.5-284 runs 2970 FPS with 140 Berger Hunting VLD's. The deer if have shot out to a max of 1000(998) yards dropped like they were electrocuted. Full penetration on broadside shots, one inch entrance wound, 2-3inch exit with major internal damage. Based on these results, I would take a shot out to 1100 yards on white tail if the opportunity was presented, and conditions were optimum.