Casing,
N540 should give you the highest velocity, and will quite possibly be one of the more accurate powders in this combination as well. From the V-V 9th Edition Reloading Guide, you should be able to start at about 32.1 grains of N540 with a 50 grain bullet, wirking up to a max of about 35.8 grains. Top end velocity should be about 3,625 fps. With the 55 grain bullets, you should be able to start at about 31.3 grains of N540, and work up to a maximum of about 35.3 grains for a max velocity of 3,560 fps. These loads were developed with Lapua's 51 grain HPCE and 55 grain FMJ bullets. Using another make of bullet, just start down a the bottom load and work up from there.
