As of 1998 it was 17,000 PSI and 20,000 PSI.
As of today it is 17,000 PSI & 18,500 PSI.
That is confusing to me. I have read that +P went from 18,500 to 20,000 psi in 1994 and is currently 20,000 psi. I remember charts in the early 90's listed 18,500 psi and currently list 20,000 psi. When did it return to 18,500 psi?
Going to the SAAMI website I find they currently list Maximum Average Pressure for .38 Special plus P as 20,000 psi.
http://www.saami.org/specifications_and_information/specifications/Velocity_Pressure_CfPR.pdf
I guess the real question mark comes with the 1974 rating of 22,400 CUP compared to the current 20,000 psi which coincidentally also measures at 20,000 CUP which is, indeed, lower than the 1970s and 1980s.
So, was the 1974 +P at 22,400 CUP significantly "hotter" than the current +P at 20,000 psi/20,000 CUP? It would seem it may have been as people have been saying.
It's probably worth noting that the current 20,000 psi, which is also 20,000 CUP coincidentally, is still higher than the 1974 standard for standard pressure which was 18,900 CUP. Is this significant for older airweights? I do not know.
No wonder people have uncertainty regarding this issue.