I think elk hunting cartridges could start at the 6.5 PRC, 6.5 SAUM, maybe 6.5/284, but I would consider their range limited still on a quartering shot. As huntinfool18 said maybe it should start at 270 cal. Longer ranges, say past 400 yards, I would start at a 6.8 Western, maybe 270 WSM if you are using a bonded or monometal. I like the 6.8 better as it brings larger grain bullets to the table (if you compare the two as they were designed, I am sure some people have fast twist 270 WSM's out there). The good ol' 7RM will stop him in his tracks though. Put a 160 Accubond or Partition moving at 3000fps from the muzzle through his shoulder he will crumble, even at extended ranges.