“Working up a maximum load” has usually always applied to loads with centerfire rifles like the 7mm mag for example. Maximum loads have been loads at levels like 65,000 psi where pressure signs started to show. Maximum loads in pistol calibers are no where near maximum pressure but at pressures that are close to industry top pressures for the cartridges. 36,000 psi for the .44 magnum. Top loads listed in manuals will always be below those levels and is so stated in the information section if you care to read your manuals beyond just scanning the load tables. As to 4227 it has been sold with two different labels, Hodgdon and IMR. Knowing Hodgdon they are probably the same powder. In the past and maybe still handloaders would increase loads for centerfire rifles until pressure signs started to appear then back off slightly for loads for large game. But with today’s terrified handloaders that practice may belong to the good old days.