2-Piper: Think of a gun barrel like a mountain. A mountain has only one peak. Pressure decreases in a gun barrel from its peak in the chamber, just like altitude decreases as a climber descends the mountain. But the climber on the way down doesn't say "This is my current peak at this very moment." That would make no sense, because he's been higher and he's going lower. Now if he says "I started at 11,405 feet. And now, having traversed a mile of downslope, I am at 10,146 feet"--that's all very useful. We know how far he's gone, and we know how much altitude he's lost. What more do we need to know?
The problem continues to be multiple uses of a word--"peak", "maximum", take your pick--that have the same meaning. And it's easy enough to convey precisely what one means, and precisely what the shooter wants to know, without using words that are synonymous--and therefore potentially confusing. Like this: "This load produces a peak pressure of 8,542 psi at 1.06 inches from the breech. At 6 inches, the pressure has decreased to 6,342 psi, and it has further decreased to 5,063 psi at 12 inches." Because all the shooter is interested in is the highest pressure at each of those points down the bore, it's UNDERSTOOD that those readings are "local peaks", if you will. But if you say that they're local peaks or maximums, then the reader may visualize that the pressure is rising again to reach those peaks, rather than steadily declining--which is what pressure does, in every graph I've ever seen. You go up to a peak and you come down from it. If you repeat peak or maximum, then the image you are projecting is like a range of mountains rather than the descending slope of a single mountain: coming down, then going back up, then coming down, then back up, etc.
A range of mountains, each peak slightly lower than the previous one, can look like that. Pressure within a gun barrel cannot. It's one continuous descent, from one peak. The rate of descent can certainly vary, but it's always headed in only one direction.
