I built a .30-378 Weatherby for a customer a few years back who had wonderful results with 150 grain bullets. I thought I would throw this out because this cartridge has even more case capacity than the .300 RUM. He used 150 OX bullets (Barnes X bullets coated with NP3) and a monstrous charge of Thunderbird - got groups in the 1/4" to 3/8" range at velocities that I am afraid to publish here for fear of being accused of fabricating facts. It did, however, have a 27" barrel and of course had a lot of muzzle blast. This gun has a trajectory almost off the charts - sight in 3" high at 100 yards and hold dead on out to 500 yards.