High pressure "signs", especially in handgun rounds are like the "idiot lights" on the dashboard of my 1968 Malibu, when you see the light, the car is already overheated. Same as in 38 special, when you see a "sign" it's already too hot.
People who keep adding powder until they see a "sign" are pushing the envelope.
I have Elmer's book, Sixguns, and he had no way to measure pressure, was loading until he saw a sign and blew more than one sixgun apart, the 45 Colt SAA came apart to the extent that he stopped hot loading it and started experimenting with the S&W in 44 Special. From that , the 44 magnum was derived.
If the Colt SAA had stood up to Elmer's hot loadings , maybe Dirty Harry would have had a 45 magnum!
Gary