I also shoot a 264 Win Mag, can you share with me your loads for your 264? How are you getting over 3,300 fps with a 140g bullet? I am very interested.
Thanks,
Big 17
My rifle is a Ruger Model 77 MK II with a McMillan (now Wisener) 26" barrel. I specifically asked them to give it a long throat so I could seat bullets out further than normal, which they did a perfect job of.
The load I use is a R-P case, Rem 9 1/2 M primer, Nosler 140 grain Partition, and 76.5 grains of H870. Chrono readings avg 3,311 fps, with a standard deviation of 16. This load is a bit over the "max" listed in the Hodgdon (73 gr) and Nosler (74 gr) manuals, but under the "max" in the Hornady (78.3 gr)manual for their 140 grain bullet.
For anyone with a standard throated rifle, I'd recommend starting somewhere around 65 grains of H870 and working your way up in no more than one grain increments. Since this cartridge is rather overbore, things can happen quickly and decisively at the upper end of powder charge range. Be careful.
With a 24" barrel, you should easily reach 3,150 fps with 140 grain bullets, maybe even 3,200.