240 gr. SMK -- .711
Posts here seem to indicate guys can get it to around 3000fps out of a .300 RUM.
I've plugged that into the computer vs Shawn's .338 Edge loads published on his site (300 gr. SMK), and the ballistics/wind drift are virtually identical out to 1000+ (though I'll grant the .338 carries more energy).
I've read accounts of it getting the job done on Elk at long ranges, though that point is probably more disputed than with the 300gr .338 version or with the Berger 210.