With today's premium bullets, any one you find commercially loaded for the .300 RUM should work fine. If you can find a copy of the Oct '02 Shooting Times there was an excellent article on the existing premium bullets with just about every paremeter discussed. I've used Federal Premium ammo in a .30-06 before switching to a .300 RUM.
Like the comments above, the 180 grain NP worked flawlessly on the two bulls I've taken.