If your shooting the traditional 22" barrel then H4895 is one of the better powders. I use 42grains behind a 147 or 150 grain FMJ which gives military ball velocities. H322 will work, it's just not optimal for the longer barrel. H335 is about the same in burn as H4895, but I would check Hodgdon's web sight for load info. The M14 is designed for military ball which is lighter than modern civilian .308 ammo so I wouldn't load to max, a grain or two under would be better. You can also look at TAC, it works well in the M14, I use 42 to 42.5 grains with a 147gr FMJ.