This is the same article I have that shows the load details of that cartridge. The whole point of its design was to get the stated velocities using stick powder at sane pressures. Ball powders that clumped up from the heat didn't make the cut. That same magazine has a section on the .458 WM that details the problem Jack Lott had with a cape buffalo that was shot by Wally Johnson, with dire results and led to the .450 G&A Short.
