If for some bizarre reason the MK do not shoot for you, try the 140gr SST. The construction is well proven and has a very high BC (1.5"long). From the 6.5-284, I would expect muzzle vel to be in the 2900fps range so any shot out to your max range would be effective.
I am working with them in my 6.5 Mystic and they stabilize in my 1 in9 twist barrel.
Dantec, from what I have read, the Scandinavians shoot lots of moose with the 6.5X55 swedes each year. They shot them at relatively short ranges because they hunt from stands with others driving the animals to them. Very wooded areas too. I don't think they are allowed to shoot over 200yds (?).
There is an ongoing saga of hunters who have killed "dinosaurs" with 243's and others who couldn't break down a 65lb doe with a super magnum and the newest premium bullet. My hunting experience shows that as long as the heart or lungs are damaged sufficiently, the animal will eventually die. The big problem is that most species, like elk and whitetail, are tenacious and can survive a very long time without either or both of these organs.
That leads to the conclusion that maybe I didn't hit them hard enough (the rush to bigger and bigger magnums). Except for taking out the spine or brain, there is no hand held calibre (legal to hunt with anyways) that is going to drop an animal every single time with a boiler room shot. With well placed shots, the best we can expect is that the animal expires within easy tracking range. Or else, we go for brain/spine and "shoulder" shots only and that opens its own sets of problems.
Jerry