Because of the limited capacity in the H&H brass, when I had the chance to convert an extra 375 to 375 Ultra, I did it. The RUM case gives you the leeway for a heavier bullet if you choose and gives the 300 grainers a bit more steam traveling at a true 2600 f/s +. You don't always have to run at full blast as you might wear yourself out and burn out the throat of your rifle. Just look at the Weatherby shooters, if they used nothing but full power ammo, their rifles would last about 2000 rounds or less before having to re-barrel.