I don't believe I have done one of these jobs on a .300 RUM yet - but the .30-338 and .300 Win Mags will do it, and so will the .30-378; as well as a bunch of smaller calibers. The .300 Weatherby, at least for me, has not been capable of this level of long range accuracy for some reason. And one of the best calibers for this long range precision shooting is the 6.5-284.

A lot of attention to detail needs to be put on the reloading process - sorting cases by weight, outside neck turning, primer pocket and flash hole reaming, bench rest primers, and lots of tweaking. And every gun, to some degree, is its own little world in terms of what it will do with certain loads - no matter how much you spend on it.