I load both Nosler Partitions and Nosler BTs for my 300 RUM. I use 80 grains of IMR 4350 with a Fed 215 Magnum primer. I use a cartridge overall length (OAL) of 3.600" for both bullets. The accuracy for both is less than an inch so I have not played around with the cartridge OAL yet. I probably will in the future. However, I'm retired and therefore don't have much free time from my fishing, hunting, shooting sports and fishing rod building.