Given the firearms were designed with the assumption that 50,000 copper units was 50,000 pounds per square inch, it just makes sense that once they created more sensitive and accurate measuring devices, they would have to rethink their load data. If the piezo electric data showed that the old load that produced 50,000 CUP is actually 60,000 psia, then the load data in the books is going to have to come down, because you are over stressing the as built weapons on the market.
That's what happened, but the data in the books didn't HAVE to come down, they
chose to go that route.
Its a numbers game, and it doesn't matter if you use CUP, LUP, PSI, Kg/cm2 or any other units, the pressure is what the pressure is. If you have proof, (like say 40+ years of people safely using load X) and the new "accurate" pressure measuring system shows 60K with what you thought was 50K, it doesn't change the fact that the gun & load were SAFE!!!
Safe at 60k as measured by the new method. They had two choices, the one they chose, keep the old limit NUMBER and measure it under the new system (which reduces the max allowable load), or raise the allowable safe pressure limit to be in line with the new measurement methods.
Many often state how "pressure signs" on cases and primers are "unreliable", and in one way, they are, but in another way, they are the ONLY reliable thing.
If you are looking for a certain sign at a certain designated pressure level, then the built in differences between all the different factors (case, primer, powder, chamber fit, etc.) make them unreliable. Meaning different combinations will not always show the same pressure signs at a designated pressure.
However, if you don't get pressure signs, then (to me, anyway) you don't have a pressure PROBLEM, with your specific gun & load combination.
And, the reverse is also true, if you get pressure signs, at a LOWER than specified "book" pressure, then you DO have a problem with your specific gun & load.
And yes, I've seen it happen. Rare, but it does happen.
and I got rid of all my "books". I don't see any need for printed manuals anymore ...
How do you check information when the internet is down??
Or load when there's no electricity??
Just curious...