ORIGINAL: eldeguello
I'll bet that you could use MORE than 52 grains of IMR 4350 with the 180-grain bullet, and get even higher velocities, IF you could get more IMR 4350 into the case and still be able to seat a bullet!
Nosler lists the 180 grain IMR 4350 load at 99% load density, so the load is not compressed for that bullet and you would think maybe they could have added another .5 grains or so, but they chose not to for some reason.