I just ordered some Berger's to try out also. I haven't been able to find any retumbo powder locally, so it looks like i'm gonna have to order some online. I have about 3 lbs of RL-17 i would love to try but haven't read any success stories about that powder for this cartridge. I have heard good things about h100v too. I will say i have fell in love with it in a very short time. The recoil is way less than i was expecting.