And once again, instead of actually being able to answer the question, you toss out a half ass thrown together insult and ramble on to another subject entirely. And no offense, but anyone who can actually describe "adiabatic pressure" (it's actually "process", not "pressure") would absolutely be able to throw together a more well written and coherent paragraph. I happen to work in the aerospace industry, and deal with engineers daily that can, and do, just that. I'm not an expert in thermodynamics myself, but I know enough to not be fooled into believing that you are either.
Adiabatic heating is what you are trying to describe. The most common example of it is in a diesel piston engine. And it's nothing unique at all to a Webley, it's the same in nearly every spring piston gun. I say nearly because some lower powered guns or target guns are setup to have low static compression ratios and are basically designed to slam. Providing a very quick and linear shot cycle at the expense of hindered power output.
The transfer port length and diameter (it's volume) along with the swept volume of the powerplant, pellet fit, surface area of the pellet base (and it's volume!), seal braking effect and spring pressure all effect the shot cycle and how much heat is generated during it.
All of this is said and done before the pellet ever even gets to the choke. The seal doesn't care what is going with the choke, because the piston has hit home before the pellet gets to it.
Here's a little evidence to this:
I'm sure with your VAST EXPERIENCE with spring guns, you have encountered a gun that slams and also one that bounces during the shot cycle. Do you happen to ever modify the size of the transfer port in the guns that do? Because if you do, you will quickly realize that a small change in the transfer port size greatly affects the shot cycle, and it's not even dependent on barrel length.
I choke my own barrels on quite a few guns, and have NEVER.....not a SINGLE time, had any difference in shot cycle from adding or removing a choke. Proving to me that it's all said and done by the time the pellet sees the choke.
As always believe what you want.