There are a lot of possible variables that affect the answer to this question.
What rifle and how long is the barrel?
What bullet, what is it's expanding velocity and what is tit's BC?
What is the load performance?
What elevations?
At 7000' with the right load and bullet, out of a 26" barrel, it could be a 1000 yd plus elk killer, but that might be stretching it. I would say realitiically it could be an 800-900 yd der and elk killer above 3000' elevation with a good bullet and load.
IMO, when you make a long shot on game you should know what velcity the bullet will be impaciting at and at what momentum. You should be reasonably assured that the bullet will perform (expand) and penetrate.
So basically it's a math problem. Crunch the numbers and see what they say.
I can probably get close to 3000 fps using RL17 and a 200 gr AB out of my 24 3/8" barrel 300 WSM. At 5000' of elevation that bullet, at that velocity will get to 950 yds with 1800 fps and 51 lbft of momentum. The minimum opening velocity for a 200 AB is advertised at 1800 FPS. And I personally consider 40 lbft of momentum the minimum I would try to make a well placed shot through the boiler room of an elk for full penetration. So for me, since 1800 fps is the bullet's limit, that is the limit I would choose to shoot ANY big game animal, deer or elk. The Bergers have the same expanding velocity as the AB's. They have a somewhat better BC and could stretch that limit a little, but not 200 yds, based on their advertised expansion velocity.
Bottomline, you can figure this out yourself, just do the math. And of course, this assumes that rifle and shooter are capable of the required accuracy.
Good shooting,
-MR