Personally, I have never used the .264 Win Mag. However, five different hunting partners over the last 54 or so years have done so. All killed elk, and I don't remember any of them taking more than one shot. All were handloaders and they all shot Partitions, although I no longer remember exactly which bullet weights and other pertinent info. With good bullets and a rifleman who can shoot, they seemed to work about as well as anything else.
Edited to add: The first elk I saw harvested with a .264 Win Mag was a really big Wyoming bull taken with one shot at well over 400 yards. We had no range finders in those days, but two of us paced it off just because it seemed such an impressive feat at the time.
