Fella's;
One huge difference between the Speer manuals that nobody's mentioned. They will change the test guns that the loads are developed in. Therefore, there can be a significant change in the reported data.
For instance, Speer #11 had it's .357 magnum loads worked up in a Ruger Security Six, 6" barrel. Speer #12 & 13 used a S&W model 19 for load development. Look at the load data for Blue Dot powder, 125gr JHP between the two manuals. Number 8, 16.3 gr max load at 1602 fps. Manual #13, same bullet & powder, max load 13 gr @ 1333 fps.
Word used to be that Speer had gone "lawyer". Not so, what they did was change the test bed for the loads. Here's the trick, read all the data published about the load you use in either Speer or Hornady, they use real guns to garner the information, not test barrels. When they change the test platform, the data changes also.
900F