I’m a 264 Win Mag fan. I love the caliber and own two rifles in that caliber.
I have found Retumbo powder to be one of the best for this caliber. Both of my rifles are 1:9 twist however both of my barrels are 26”.
Both of my rifles shoot the 140 Accubond or Partitions well. They however excel with 130 Accubond at 3250 FPS.
They also shoot the Barnes 120 TTSX at 3400 FPS.
On my Sako I have the Leupold VXIll 4.5x14x40
On my Sendero I have a Vortex 4x27x56 Razor
The Sako is my woods rifle loaded with the TTSX
The Sendero is my open field rifle loaded with the 130 Accubond.
If you need any further feel free to PM me.