Some total guesswork I think as I can't see how you could easily measure the air other than maybe a cloud chamber and high speed camera?
Before that, I think you would have to know how the air behaves within the barrel? The pellet is not an air-tight fit so until the skirt opens up and forms a seal there will be some amount of air in front of the pellet. The pressure build up won't be instantaneous so again as it ramps up there will be some air release and possibly some pellet movement (lighter vs. heavier pellets? normal size or reduced down?).
As the air+pellet starts to exit the barrel there will be a compression wave and more or less leaked air? As the wavefront hits the edge of the stripper cone it may very well reflect back - maybe even "pinch" the air behind the pellet?
I use a break on the front simply to direct the noise sideways. If I have no shroud and no break the discharge makes my ears ring (and we are no longer permitted ear protection I think), with a shroud it makes it more of a pipe noise, with a break I don't hear it behind the gun but I daresay others to the side will hear it. Basically compare the noise a typical Steyr makes with their bare-barrel as supplied.
Nothing at all like a full bore rifle of course. I have shot 7.62mm on the Bisley ranges and laid next to someone with a heavy break on front of a hefty Remington. Just about enough time between his shot and mine (markers have to drop and raise targets) for the coughing to stop as you end up with a face full of dirt, dead grass, spent powder (and unspent). The break then eats some of the recoil and helps keep it centred but the sideways noise and blast means that some range officers tell them to remove it or leave.
I think silencers are different in that the series of internal baffles slow down the waste air behind the pellet so it comes out in a slow cough rather than a fast crack. A stripper would have to be bang on bore centre otherwise it may cause a defection (more than its weight on the end) so it could vary between rifles simply because there is no guarantee that the hole down the middle of the barrel and outside diameter are exactly concentric. hence really fine tuning could very well have an effect while bolting on a "stripper" just changes the noise and aesthetics.
All the above utter conjecture so could be a load of "something RobF's filters remove" :-)