When I first saw this, the only thing that came to mind was 7mm STW. A friend of mine has one that he uses for F-class and he sends 180 Bergers at about 3200. So that has 1400ft-lbs of energy at 1000 and a drop of 212", at 600 yards it has 2200ft-lbs and a drop of 57".

Of course if you want to shoot factory ammo you will be, for the most part, SOL. I would have to recommend handloading for that sort of distance anyway, only way you will be able to get the same results consistently.