dwhite: I agree--but does anyone know just how precise the testing is, and what the specifications for precision are?--in layman's language, I would like to believe that the 'results' of the tests are better than something like "plus-or-minus five percent," but I wonder....
Add to that the repeatability factors of such testing, and it behooves all of us to remember that probability analysis is really what "the pressure numbers" are in our hobby. Taken to the extreme edge, that simply means that every shot is a new crapshoot, so to speak, and new roll of the dice.
I haven't updated my charts' downloads for the past year or so--but consider the location of True Blue (and AA#5, IIRC) on the RamShot Chart vis-a-vis the Hodgdon chart. (Not to mention the older charts no longer updated, like from Winchester.) It was when I started chasing these differences down that I began to understand that powder pressure charts were merely sequential lists, and do not represent a linear (or logarithmic, or whatever) progression.
Jim H.