back when if they didn't have any data that they just guessed. Just guessed. In one manual they got so many complaints from used that they took the remaining copies to the local dump. I'm real sure that this story is true even if it is hard to believe.
And when, earlier than the old manuals, they came up with SAAMI max pressures, they got them from Mosses?
No, they just guessed.
There had a system that worked, and then they started to try to make it more reproducible and traceable. In making changes they always errored on the safe side.
So what do you get with newer load books?
Errors on the safe side.
What do you get with old load books?
Closer to the correct answer.
Correct, in that both the error of pressure testing AND the error of the SAAMI max pressure has also been removed.
Of course someone, like Glock, could come along and make a feed ramp .250" deep, like the G20, that will case bulge at 37,500 psi.
Now dumbed down is becoming a reality.
I handload 60 calibers and I don't use load books. I make up loads. I just guess.
At the other end of the spectrum are those that like to do things per proceedures. And they should.