I have killed almost 50 elk and seen at least 100 others shot. Maybe a bit anecdotal, but all of the ones not recovered by others have been with 7mm on down. My Dad shot a cow elk at 80 yards with a 7mm Mag in the chest 3 times and the elk was still grazing. He thought he missed. I handed him my .30-06 and he shot it...bang-flop. He put a nice clean set of 3 pencil holes through the lungs, no rib hits. I shot an elk at 425 yards with my .30-06 with a Winchester 180 grain Silvertip, DRT and the bullet is sitting on my desk, 110 grains recovered between the off side rib and skin. Elk are tough and yes, placement and a good bullet are important, but it is hunting, not the range. I tracked an elk someone else shot with a 7mm Mag a few years ago, 5 miles in 10F weather, 18" of snow and with a blood trail so easy a 5 year old could have tracked it. It was a good shot right through the lungs, just missed the top of the heart. The blood and air pumps on elk put everything else to shame.
I use a .338-06 now, but my 15 year old now shoots my R700 .30-06 for elk. I limit myself to about 600 with the .338-06, furthest I have shot was 505, DRT. I would pick a .30-06 over a 6.5 or 7mm every time. The only caliber I like more than the .338-06 is one of the .375s (but I am having a 300NM built)
Take a look at the .338-06 and consider a rebarrel of one of your R700s. It is an excellent cartridge.