Other than direct pressure measurements via psi or cup. probably the most accurate (potentially) was Ken Waters' method of measuring the "pressure ring" just ahead of the solid part of the case head, to 0.0001" I suggest that you do this for your lot of brass in your gun's chamber to see what is the case expansion for "normal" pressures and if you go beyond, noted by how much the pressure ring expands. If you go too far, you get signs of excess pressure--primer pocket looseness, brass flow into the ejector cut, stiffer extraction, etc. If you take pressures far enough to get any of those signs, you are on your own and can get a facefull of gas or worse, especially at higher ambient temperatures, etc. Some of us explored the outer limits when young, and some of Ackley's recommendations treaded on that territory, especially to get more velocity from his "improved" cartridge cases. As we got older and more conservative, most of us stay a bit undeer the loading manuals' max recommendastions for a particular powder and projectile.
This old wives tales been disproven.
