I did a quick check with a 300 WSM and the 200g AB at 2900fps. It will have 1785fps, and 1415 lbs at 800 yards. I would say that would/should get the job done on elk/bears at 800 yards. Did not run the numbers for the 7mm WSM or RM, but I already know the 30 cal hits harder and retains just as much velocity.
2000 round barrel life, 800 yd Elk and burning sub 90.0 grs of powder makes cartridge selection very challenging to say the least.
You may want to consider a 280 AI. A 160 gr AB w/ 62.0 grs RL22 will get you 3000 FPS and cover Elk to 600 yds.
You will not be happy, or a real man, until you get a certain cartridge that shoots a 400 grain HPBT at 3300 fps, BC of .989, supersonic past a mile and one half. It is available, being shot right now, factory ammo.
Seek and you shall find...
The long action on your 300 RUM won't allow you to just swap tubes to use the short mag, you would be better off to just buy a 300 wsm if that's what you're focusing on, best of luck in your search.. [img]/ubbthreads/images/graemlins/cool.gif[/img]
The 6.5-06 AI is another choice I was heavily looking at. I would think it would get the job done as well. If only Nosler made a 140g AB for it. I know its a tough, but I think there will be a cartridge in there that I can put to real good use.