I don't believe that older (pre-Extreme) H-4831 would have given you this much grief. Norma used to suggest Norma MRP-2,( now discontinued) which is much slower than H-4831. Even IMR 7828 is slower than H-4831, but it doesn't have the pixie dust that gives it as much temperature resistance, particularly at low temperatures as the Extreme H-4831. I do believe that this pixie dust requires pressures in the 60,000 psi range in order for the slower burning Extreme powders to work as advertised. But the IMR 4831, and the IMR 7828, do work better in the 40,000 psi range in cases like the Nitro Express numbers, the .416 Rigby, and the .505 Magnum Gibbs.

I still stand by my earlier assertion that IMR 4831 and IMR 7828 would be my first choices for powders with both 525 and 600 grain bullets. IMR 7828 is listed in the Barnes manual for use with their 525 grain Banded Solids, and their Triple Shocks. 90% plus loading densities in each case.

It may be me being superstitious, but I personally would avoid compressed loads in this cartridge. Just enough room to hear the distinctive tinkle of powder jiggling in the loaded case would calm my nerves before taking this cartridge into battle. A sort of final , final, final check.