Mathman, I totally agree. Even with powders that don't get the fastest velocities, the .264 is not a belted, oversize 6.5x55!
I've played extensively with two over the years, the first a genuine pre-'64 Model 70 Westerner with the original 26", 1-9 twist barrel and the second a special run of Ruger Hawkeye stainless/synthetic with a 24", 1-8 twist barrel.
The Model 70 came along before some of today's newer powders appeared, but its best load with 140-grain bullets (which I prefer in the .264) was 69.0 grains Ramshot Magnum, for 3225 fps and sub-MOA accuracy. With the 130-grain Barnes TSX the best load was 66.5 Accurate Magpro, for 3311 fps and similar accuracy.
In the Ruger the best loads were the 130-grain Nosler AccuBond and 70.0 grains of Ramshot Magnum, for 3256 fps and groups averaging around .6 inch; the 140-grain bullets the powder charge that got the fastest velocities was 63.5 grains of RL-25 for around 3100 fps, and sub-MOA accuracy with several bullets.
But if I didn't have those powders would certainly be willing to experiment with what the OP has, especially H4831 and RL-26 with 140s, and H4350 with lighter bullets.
