Use OCW or ladder test to find an accurate load for your rifle.
Seems like ladder testing is losing favor to OCW these days, though.
Directions for doing either test are easily enough found with a Google search.
It's also imperative that you determine the maximum for your chamber/brass/primer/powder combination.
I do this at the same time I'm running the OCW, but it can be done beforehand in a separate test.
Doing it during the OCW saves time, components, and a little barrel wear...
I start at book minimum and load 3 each in .2 gr increments for .223 like case capacities, .3 gr for .308 like capacities, and .4 gr for .300 WM like case capacities.
I write the charge on each case, in case the ammo box falls over over or some other calamity (stupidity?) mixes them up.
I load up to and beyond the book max by 2 loads, in case my chamber is especially tolerant (long throat, etc.).
I am inspecting every case (well, maybe not the cases at book minimum or thereabouts) after firing, looking for first primers flattening and cratering, then ejector swipes, and monitoring for other signs like difficult bolt lift, etc.
I might not even make it to book max before I declare my max charge, or I might end up shooting everything up to and including 2 loads above book max safely.
When I'm done I have my max charge and OCW results.