Originally Posted by MaciekA
I think you would need to back this claim up with evidence and have other people able to reproduce your test. Off the top of my head you'd also have to ensure your chrono is at the same distance from the exit of the barrel in each case, in order to ensure your results were accurate. Until then, I'm going to challenge this claim.
It's fairly well-established on other more technical airsoft forums that "barrel suck" doesn't exist, so it's extremely unlikely that "suppressor suck" exists. Again, we are talking about your BB usually clearing the length of your suppressor tube in well under a millisecond -- there's really nothing about the interior of the suppressor that is different from the air it travels through once it is out of the suppressor.
I don't think the fluid dynamics of air allows for any "wake" or pressurized suck to catch up with the BB before it exists out of the suppressor. I could be wrong if your argument is that the sound wave would cause some kind of friction, but that sounds crazy, no pun intended
I'm definitely not claiming barrel suck, as once the BB is in larger diameter area I can't see it effecting it; unless air rushes back in the end of the barrel after the BB leaves to fill the vacuum. A backdraft could maybe affect or mitigate a small amount of BB back spin; but I'm not seeing that being the case. As you say, the velocity has the BB leaving the barrel in such a short time that velocity or spin shouldn't be affected.
It's more likely a sudden pressure change while still inside a small area. The air that the BB pushes out the end of the barrel may not be able to disperse quickly or evenly as it slams into the suppressor. Suppressors do after all absorb sound and shock, that may also have something to do with it.
I do know I'm not the only one who has seen this effect. Maybe we go shooting next time, we'll see if there is a consistent FPS change up or down (if any).