In Hornady's pressure testing during development of their new .450/.400 3" factory ammunition, 82 grains IMR 4831, Hornady case, Federal 215 primer and 400 grain Hornady soft point bullet produced 44,000 PSI. The CIP (this cartridge is CIP standardized, not SAAMI) maximum permissable average chamber pressure for the .450/.400 3" is 40,610 PSI. Different brand case and bullet, but that load is almost certainly over the top.