I have tested h1000, retumbo, and rl26. I have n565 coming. A buddy has some 4831 to test. My barrel is 22" so a little faster powder seems to work better. Right now RL26 is the best choice and H1000 is in the running but not as fast. I have used rl26 in many cartridges and it is my favorite in 6.5-284 and 6.5 creedmoor. Retumbo works well in longer barrel applications and this short barrel PRC doesn't like it that much.
Personally I see H1000, 4831, 565/570, and rl26 as winners. I won't mess with temp sensitive powders so I don't know how they do.
Right now my accurate nodes are as follows:
156-55.5 rl 26 @ 2900
135A-58 rl26 @ 3090
143-56.5 rl26 @ 3000.
Yes, some higher charges are producing better results but I am getting a bolt lift click at the top of the stroke that bugs me. None of these produced ejector marks.
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