Re: 308, 7RM or 300RUM best for 1000 big game?
After owning a couple 300rums and 30-378 I wouldn't give you ten cents for a truck load of them.
With the right bullets, the 300 win mag is all you need and is MUCH easier on barrels. At elk altitudes the 210 ALR can get you to or over 1500'pounds of energy at a grand. Plenty. The 300wm is not my favorite caliber but if all I did was hunt elk at long range, it would be my rifle of choice. I have a Sendero 300wm in a McMillan stock. It is a sweet shooter. Very accurate and easy to clean.
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.