From the SAAMI Technical Data Sheet: Maximum Average Pressure--is the recommended maximum pressure for loading commercial sporting ammunition. Slightly different words, but it's the same thing the CIP refers to as their standard service pressure.
Completely misleading. The Maximum Probable Sample Mean (MPSM) is, the maximum expected average pressure that may be observed in the testing of product subsequent to its manufacture .
The MAP is the intention; the MPSM is the acceptable reality when a lot is tested prior to release for public sale.
Your problem, gun rag writer, is that you want things to be simple. When they arent you just start ignoring facts until its simple enough for you.
Anyone who is truly interested in this subject doesnt need to take my word or Larrys. The actual facts are published by SAAMI.
Found any of those pre-WWI Spanish guns yet, Kyrie? Photos maybe? To include details? I find it interesting that Spain did not even adopt obligatory proof until 1924. And that before things became more "standardized", Spanish makers were in the habit of copying proofmarks from other nations. Might explain why not many of those guns made it out of the country.
Asked and answered. Apparently you didnt like the answer and would like to pretend the answer never happened. Shrug.
