Quoted: the gas tube directs the gas towards your face to drive the bolt carrier group rearward, the upper reciever is not a seal tight set up and after the bcg goes flying rearward the rest of the gas gets blown rearward as well. what is directly in the path of the gas tube? the charging handle and your face.
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The charging handle on all five of my ARS latch securely against the upper receiver. While not an airtight seal, it is certainly a solid blockage against pressurized streams of gas or particles. As soon as the bolt carrier clears the ejection port, gas takes the path of least resistance and ambient receiver pressure drops to equilibrium with atmosphere. I occasionally get a smell of propellant, but never had any particles.
Additionally, if that WERE true, vent holes in the SIDE of the charging handle would possibly relieve a little more pressure, but WOULD NOT magically redirect this stream of gas...unless by making holes we somehow obtain the gas tight seal you note isn't there?
I've used 11.5" military carbines and not had the described problem. Spoke to a SEAL who use suppressors, and he has not had the described problem. I'll keep asking, and I've got an inquiry in with someone who can describe the pressure curve in the barrel and gas tube better than I can.
I can't think of a way to post the relevant equations for cyclic pressure pulses here. I'll see if a aeronautical engineer I know can model it real quick and post a link for the curious. However, the described problem is neither common nor easily described, given the non-cylindrical shape of the plenum involved, and a "solution" to said problem would involve (as was noted upthread) an expansion chamber in the gas tube to moderate the waves, or a change in gas port size.
I'm really trying to visualize a solution involving vents in the charging handle. Said vents would reduce mass and create stress risers that would weaken the charging handle, and would lead at best to a faster drop in receiver ambient pressure to atmospheric ambient. It could reduce the pressure pulse in the immediate volume around the gas block. However, as soon as the gas block (with the bolt carrier) has cleared the front end of the charging handle (which for purposes of the firing cycle is a fixed component), gas will immediately flow into the entire receiver volume and magazine well. Additional holes in the charging handle do not appear to be of particular advantage to this event.
I'm trying to find a practical reason for this device, but so far, I'm coming up with marketing BS.
Looking at PRI's other accessories, I don't see anything of significant use I can't buy cheaper elsewhere or do without.
But your mileage may vary. That's why the pic threads have 400 different variations built on the same receiver.