the accubond LR's were(are?) grossly exaggerated in the BC department last I heard (especially 6.5mm)
as for expansion at 1300ft/sec nosler has a picture of how well it expands over a broad spectrum of velocities. although the bullet expands down to 1300ft/sec that doesn't exactly mean its maximum or ideal, also you have to remember that's the threshold in which they see expansion and it's not guaranteed.
lastly
my rule of thumb is I wouldn't hunt at a distance where I cannot keep 3 shots on a paper plate (10" target) using field shooting positions. look at how much that bullet drifts at 1200 yards in the wind at say a 10mph wind. now check it again at say 7mph and see how extreme of a difference it is. most shooters couldn't tell the difference between a 5mph wind and a 10mph wind. I said 3 as a seasoned shooter may be able to gauge wind within 3mph.
That's all assuming the wind is constant. 1200 yards is a good stretch and dependent on terrain you could have 2-3 different wind directions and speeds from the shooter and target.
I closing I feel an ethical hunter would choose their shots wisely within their personal capabilities(and not based off "oh one time I did it at XXX distance so I'm golden" it should be what your capable of doing consistently) and shot placement trumps energy always. not to say energy isn't important. so if long range hunting is something you'd like to persue I'd recommend getting a lot of trigger time and also choosing the right cartridge for the quarry. BC will be your friend as the better the bullet bucks the wind the better your odd's of putting rounds on target where you want to put them.
another thing that would further help would be to have a buddy setup a target at a unknown distance then climb a hill or jog 20 yards to the shooting position anything that will elevate your heartbeat and disrupt your breathing then put yourself under the gun. give yourself say a 2 min time frame to, laser the target, dial in your dope, find a shooting position to steady yourself calm yourself and control your breathing oh wait did you even factor in wind? and lastly make the shot. it's a lot harder than you think and I can promise you the real deal is that much more of a high and a lot of the stuff goes out the window when you have that animal in your crosshairs.
Here is the standard accubond expansion photo I mentioned. doesn't show that on the LR page. I'd be willing to bet it's very similar.