Re: 264 mag. which powders to start out with ?
I have had very good luck with IMR4831, 140 bergers, FGMM primers and 7mm rem mag norma brass necked down. This combo has worked well with a couple different barrels. Velocity is 3250 fps. H1000, H4831sc and IMR4350 are also good choices depending on what bullet you choose to shoot.