I can't comment on the 300-MP, never used it, though I'd love to here some loads for it. I've thought of getting some 300-MP since I heard about it.
I can comment on the 300 grain XTP though. I load 21 grains of H-110 with a CCI 350 primer. I use the first cannelure to crimp in, that is the one closest to the top of the bullet. My little Pact Model 1 XP shows I'm averaging around 1180 fps from my 5.5" Super Blackhawk. When I tried the same load with the bullet seated in the last cannelure, it only developed around 900 fps from my 6" 629-6 I used to have. I realize its not a very good test, being to different guns and barrel lengths, but it seems to develop less pressure when crimped in the bottom cannelure.
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