Ultra heavy loads aside, my BRNO .358 NMag. absolutely thrived on IMR3031. Seems to me the load was 62.0gr. with Speer 250's for around factory ballistics - 2,700fps.

With a 12X scope mounted, I beat a 6x47 bench rifle, group for group, one whole day - while shooting at 100 yards. My largest group was 3/10" on centres, while most were 1/4" and smaller. Both Alex & I were astounded as to the accuracy of that load. Nothing else was consistant at below an inch, but many other loads goruped around an inch. That happened in the early 70's, when a rifle that was a consistant 1/4MOA gun, would win Bench Rest matches. This rifle, with that powder only, was capable.