Hounddawg,
I suspect, as I have when I've brought up conflicting looking Hodgdon data to them before, you may get a reply back stating they have a ballistic technician's signature on a test document showing those numbers are what he got.
It is odd data, though. According to Bryan Litz, the 140-grain Amax and the 142-grain SMK are both 1.375" long, yet that data has the A-max seated longer and lists a 40-grain charge as compressed, while the SMK is seated shorter and lists 41.5 grains as not compressed. So either two substantially different lots of H4350 were used or the case lots were different and had substantially different capacities. Both are possible, but whatever caused it, clearly an apples-to-apples comparison was not being made.
The load developers go to some trouble to try not to publish bad data, but it happens. Typically, the bullet makers seem to develop most of their loads in production guns, looking for pressure signs, and then have only the top load tested for pressure (to save money) and the rest are estimates. If one of their measured maximum loads has even a single round that goes over the SAAMI MAP value, they lower it. This seems to be a fairly universal practice and is described in detail in the last of the printed ring binder version of the Hodgdon manual. It is not how ammunition makers use the SAAMI limit, though, which is as a limit for the average of ten rounds, where the handloading manuals written today treat it as an upper limit for any member in the sample.
Hmonnier,
Using powders that are too slow can ring or bulge a barrel. They also ignite poorly, leave a lot of fouling, and require heavier charge weights to achieve a given velocity. The powder should be matched to the gun and the bullet.
The way I pick powders is to look at Hodgdon's data and at the peak pressures listed for each. As they explain in their print manual, because they size the loads so the worst case high-pressure cartridge in a sample does not go over the SAAMI MAP number, the powders listed with the highest peak pressure numbers are the powders that had the lowest pressure variation in their tests. That's a good sign ignition was consistent, and those are the powders I would look at first in the range of fast to slow.