I think JB used the Magnum primers because Ramshot listed them, albeit mistakenly (I'll have to re-read the article and check that, don't want to speak for him). JB achieved some nice velocities though, so maybe it's worth trying. I'm going to start with my standard BR-2 for now. But, I do have a couple hundred 215s sitting around all bored... Edit: I think I'll work up the 185 TTSXs with BR-2s and 215s at the same time. See what happens...
