I think so. When I lived in Maine I hunted deer with my .243. Although I never got a shot, I visited a deer camp where there was a deer hanging from the rafters that dressed out at 240, so about 300 on the hoof. I looked at my little .243 100-grain round and thought, "Nope, not enough for that horse." But, that long 6.5 bullet would be just fine.
I remember the old Finn Aagaard tales of people taking elephants with the 6.5 x 55. Of course they were expert shots and put it right in the ear hole. But, the 6.5 has a reputation for unworldly penetration. In the .260 Remington, 1500 ft/lbs. out to 250 yds, so adequate for elk out to that distance and anything but grizzly to ranges beyond, with low report and recoil. An amazing cartridge. "Sweet spot".
Would you figure something like a Nosler Partition in the 260 for elk, big bodied deer?