OK, now I've got it. But I'm a word guy, and you techie types are still spreading confusion with the use of "peak". Pressure only peaks at one point in the barrel. Whatever the pressure is 6" or 12" or 18" down the bore, it ain't a "peak". It's just the pressure at that point. Look at it in reverse: a car accelerating from a stop. If it reaches 25 mph in, say, 3 seconds, that is not the "peak" speed of the car, unless it stops accelerating at that point. That's just its speed, as measured at that point. Peak is not reached until the point at which the car ceases to accelerate. Same for pressure within a shotgun barrel, but in reverse. If you use "peak" for anything but the highest pressure measured, I can guarantee that you will seriously confuse the non-techie public. It will cause them to believe that pressure within a barrel works like this: ^^^^^, going up and then back down numerous times, rather than like this: \.
