BCSteve,
I've been a believer in the .264 bullet at moderate velocities for the killing of game from bull elk and bears down to deer for years.
Your efforts and documentation are excellent..ought to be a sticky..:)

I always used wet phone books, covers on, after soaking in a clay surry for a week for my tests back when.

I also shot at 50, 100, 200 and 300 yards.

That told me something about the bullets and loads I tested which were for big gasme in the lower 48...at my own hunting distances...which were always closer than 300 yards..

Worked the chrono also and only loads and bullets that would shoot MOA from a rest from my rifles were bothered with.

Hard to beat the 139-140 grain bullets in the .264 running at 2500-2600 fps MV for penetration, accuracy and killing efficacy on game bigger than a shepherd dog..:)

The Swede 6,5x55 is my only experience with the .264 bullets on killing..
Because that worked..I never 'fixed' anything..:)
Best regards, Jim