From my experience Berger's numbers tend to be very conservative.Well I wasn't able to get to the range these days off to shoot unfortunately. I have a few rifles to shoot so I need to get out for sure.
Heard back from Berger today and they had more info.
264Win Mag 156 Berger EOL 26" bbl 3.340" COAL
He didn't mention which primer and didn't think to ask
RL23- 56.5 2745 fps
59.3 2854 fps 90% case fill. Max
H1000- 61.5 2796 fps
64.6 2934 fps 97% case fill. Max
Retumbo- 64 2829 fps
67.5 2975 fps 100% case fill. Max
They did not or would not try RL26 due to too much empty space left in case and didn't want to chance a potential detonation.
I would expect better velocities than shown there unless you have a short tube.