IMR-4831 or RL-15 are both excellent powders for the 450-400..I settled on RL-15 because of some so called problems with IMR-4831, that I have to this day been able to substanciate, so put it aside as rumor and BS..but to err on the right side I went with RL-15 anyway

BTW, the world of the double rifle is busting open with myth, black magic, inuendo, and rumor, some even thrive in it...but in reality most of it is nonsence....