No load manual published has had loads that were above the original pressure maximum for the round. I can't think of one that won't allow you a safety margin of 1000-2000 PSI or CUP. I use the SPEER #11 and Lyman 46 for most of my magnum revolver and rifle loads. Not one hasn't been safe. As an example, 9mm data up until the 80s was 35,700 CUP. SAAMI reduced it to 35,000 PSI and then we saw the introduction of +P ammo that is identical except that the measurement system changed to PSI. 38500 PSI which is the limit for 9mm +P is nearly identical to the original pressure spec of 35,700 CUP. What has changed is a society obsessed with liability litigation. As far as magnum revolvers go, many loads are being published again with load data for .357,.41 and .44Magnum that go up to or slightly above 40,000 CUP. About the same data you'll find in older manuals. A lot of this was brought about by imported firearms that were less than excellent quality. And, some of it can be blamed on the S&W M-19 that was designed for continued use with .38 Special with the use of .357 Magnum limited to carry by police officers. Many did not heed the warning and used full house load data for their K-frame and they got split forcing cones for their misguided efforts.
The one factor that can change is powder. That is why EVERY load manual will tell you to start load development from a start charge when you change to a different lot number of the same powder. This is a valid caution. All you need do is go to the Alliant website and you'll see that there was a recall for Unique a while back. In this case the wrong powder got placed into Unique containers. A number of powders have had fluctuations in burn rate characteristics over the years.
And then there are different ways of measuring in the piezoelectric system. There is info worth reading in the Lyman manual. Many powder companies continue to test by copper crusher. In the CIP system the Europeans use, the resulting PSI values are very close to CUP measurements. Vihta Vouri's early load guides provided CIP pressure ratings that were close to our pressure specs in CUP. Vectan did as well.