Aviator,
The maximum loads listed in manuals are normally quite safe these days. Forty years ago they were sometimes not so safe, but today all the manuals only list pressure-tested data, and unless a rifle is custom-made with an off-standard chamber the max loads are quite safe, as long as you stick to the same make of bullet listed.
Your H4831 experiments sound like they ended on the light side. One of my standard loads for the .300 Winchester is 75 grains of H4831 with about any 180-grain bullet. This often isn't quite as fast as with some other powders, but it does usually get around 3000 fps and is very consistent in a wide range of hunting temperatures, while some other powders are not. This is a characteristic of the Hodgdon Extreme powders.
