Best Overall 556 Can

[Failure2Stop]

This is what I was getting at, but not asked in the clearest way...You obviously have to have gas pressure to operate the system and it's impossible to have 0 gas blowback if you want to keep the semi from becoming a bolt gun, so if I'm going to use proper buffer springs/weights and tune the gas pressure (BRT gas tube for example) to run the system just inside of that threshold to maintain reliability but not be overly gassed, then what does the newer "flow through" tech give me that a standard can doesn't? Wouldn't that have roughly the same effect?

When it comes to suppressing a gas-operated firearm, the residual bore pressure that results due to the containment and slowed release of the pressurized gasses inside the suppressor is responsible for speeding up the extraction and ejection phases of the cycle of operation, which can cause issues in ejection and increased cycle speeds. The escape of those gasses also contributes to significantly increased exposure to lead and toxic/noxious gasses and fumes for the user. This is not talked about nearly as much as it should be, but those of us in the suppressor industry have been paying attention to it over the last few years when testing has illuminated the issue.
There are a few ways to remedy these problems. When it comes to the operating system itself, you can reduce the pressure to the point that the primary operating system barely does more than unlock the breech mechanism, relying on the blowback effect of the contained bore pressure to complete the rearward stroke. This, however, will make the gun severely undergassed in an unsuppressed configuration. You can increase ejection force, as KAC did with the E3.2 bolt, but that won't slow down the operating system, so you could still have issues with the magazine keeping up with the cyclic rate. The optimal approach is to use a low backpressure suppressor that keeps cyclic rate increase to less than 10%. That not only keeps the operating system working in its optimal band for reliability and felt recoil/muzzle rise, the will also significantly reduce the increased exposure to the nasty stuff that usually gets blown downrange instead of sitting in a ball around two of your most important orifices.

[markm]

contributes to significantly increased exposure to lead and toxic/noxious gasses and fumes for the user. This is not talked about nearly as much as it should be,

Snipped and quoted for emphasis. I can't tell you how eye opening it was for me to see the toxic cloud sitting in the bore when I popped the action, removed the BCG and looked down the barrel. A nasty cloud of toxic gas so thick you literally cannot see light at the end of the barrel.

If suppressed AR shooting was an OSHA overseen activity, the PPE and ventilation requirements would be staggeringly extensive and expensive.