Well, CIP maximum is generally lower than SAAMI maximum so to get any decent performance CIP shells appear to need to be loaded closer to maximum peak under their standard.
Interesting discussion. We probably need to start with the obvious, which is that there is only ONE peak pressure, and that occurs in the chamber. Pressure doesn't start high, drop, and then go back up. It drops all the way from the chamber to the muzzle. The only difference is in how quickly it drops. Different pressure curves . . . but they're all headed in the same direction.
And it's quite possible to obtain "decent performance" from shells that are loaded well below max service pressure. We don't care what the pressure is at the muzzle. We only care about sufficient velocity to give us sufficient energy (and penetration) to do whatever we want the load to do. For several years, I've used a reload for pheasants in a Federal hull with Fed wad and primer, 22 grains Unique, 7,200 psi. That's well below both SAAMI and CIP max service pressure. Yet it yields 1200 fps velocity at the muzzle . . . and the pheasants don't like it at all. That load may well retain a higher pressure as it moves down the barrel, relative to peak pressure, than does a load that generates 11,000 psi peak pressure. But performance, based on my field tests, is definitely "decent".
