Does anyone actually carry 175 grain bullets in the 7 Mag? For some reason I've never considered the 175gr .284" as the equal of the 180gr .308" bullet. Always seemed to me that the heavy bullet types shot a 160 in their 7 or 180 in the 300. It was only the guys that insisted on a 220 grainer in their 300 that would use a 175 in their 7. I'm a big 180gr fan in the 30-06 or 300 but I can't imagine wanting a 175 in my 7 Wby even though they should be essentially the same. Maybe it's some ingrained perception that the 7 is meant to be used in even more open country than the 300 and thus you would want the best balance of speed, momentum and BC. Of course, I'd also seriously consider loading a 140gr bullet in the 7 but wouldn't even entertain the thought of a 150 in a 300 WM. Funny how a fellow gets something in his head.
Now the 264...well, it has the advantage of sharing a bullet diameter that is currently favoured by a very rabid long range community so you know that everyone is coming out with an ultra-slippery 129gr bullet. But does that necessarily translate well to driving a bullet through the ribs of a moose or elk at 300 yards? Maybe. But I'm always skeptical of the integrity of the bullet when you start narrowing up the diameter. Example, the 270gr .375" Sierra Gameking was regarded as a damned fine bullet. Not a premium, but it punched well above it's weight. But does that particular Sectional Density (.274 which is pretty close to the .264 for the 129 grain .264" bullet...the 260gr .375" bullet is identical at .264) tell the whole story? When you diminish the frontal area by 50% you have to make some sacrifices in a jacketed bullet to maintain tolerable dimensions. I always wonder is a narrower bullet will have the toughness, probably why I lean toward larger diameters.
So, if I was an open-country deer, antelope, or caribou hunter or I enjoyed using my hunting rifle for predators I wouldn't balk at the 264 for a second. And it might be the greatest sheep and goat caliber ever devised. But if you want to throw moose and elk into the mix and certainly ursus, Well, I'm a dude that likes more. I find that more is rarely unwelcome.