...so, I am going to preface this by saying that I am first and foremost, an utter amateur in the world of semi-automatic firearms. As such, I may communicate thoughts or concepts that are ridiculously simple or even completely wrong; and for those of you who have more knowledge/experience than I do, I would appreciate constructive feedback rather than simply being called a dumbass. That being said, I recognize that this is the Internet, so I'll go ahead and do the work for you: I'm a dumbass, but I'm trying to learn... and I can use all the help I can get.
ANYHOW, on to the subject matter... adjustable gas blocks (specifically, on AR-pattern rifles). Most AGB designs of which I am aware restrict not gas pressure, but gas volume; the restriction of pressure is a side effect of the volume restriction. That is to say that the DI system on an AR-pattern rifle has a given volume that is, while the rifle is at rest, at atmospheric pressure. As the rifle is fired and the projectile passes the gas port, the high pressure gas that is chasing the projectile out of the barrel looks for any way it can find to move towards a low(er) pressure area... so, the gas system. As the gas system is (rapidly) filled with combustion gas(ses) from the deflagration of the powder in the cartridge, the volume of the gas filling the operating system quickly exceeds the (natural/atmospheric) volume of the operating system; as a result, pressure within the operating system builds. By restricting the volume of the combustion gas(ses) that enter the operating system of the rifle, we also restrict the pressure of that gas simply as a side effect of stuffing less gas into a given space. Pretty basic, right?
With that out of the way, I don't see why a self-regulating adjustable gas block/system could not be constructed (I'll freely admit that this is where my lack of knowledge will really be apparent). I am envisioning a design with two, sequential gas ports; the first being used to push against a spring loaded valve that restricts the passage between the second gas port (which would actually provide the gas to operate the rifle) and the rest of the operating system. Conceptually, this valve would, at atmospheric pressure, leave that passage wide open, thus providing no restriction to gas flow between the second gas port and the rest of the operating system. As barrel pressure increased, the valve would push harder against its pre-load spring and close off more of the passage between the second gas port and the rest of the rifle operating system. The self regulation function is evident at this point... the less gas pressure there is in the barrel, the less gas pressure there is to "choke" the passage between the second gas port and the rest of the gas system, and the greater the gas pressure in the barrel, the greater the effect on the spring loaded valve and therefore the greater the "choke" on the gas passage.
I'm certain that I'm not innovative in this thinking... there are enough people who have a hell of a lot more knowledge/skills than I do, and such a system does not exist today (that I am aware of). I can therefore only conclude that there has to be something that I am overlooking; do any of you know what that might be?
ANYHOW, on to the subject matter... adjustable gas blocks (specifically, on AR-pattern rifles). Most AGB designs of which I am aware restrict not gas pressure, but gas volume; the restriction of pressure is a side effect of the volume restriction. That is to say that the DI system on an AR-pattern rifle has a given volume that is, while the rifle is at rest, at atmospheric pressure. As the rifle is fired and the projectile passes the gas port, the high pressure gas that is chasing the projectile out of the barrel looks for any way it can find to move towards a low(er) pressure area... so, the gas system. As the gas system is (rapidly) filled with combustion gas(ses) from the deflagration of the powder in the cartridge, the volume of the gas filling the operating system quickly exceeds the (natural/atmospheric) volume of the operating system; as a result, pressure within the operating system builds. By restricting the volume of the combustion gas(ses) that enter the operating system of the rifle, we also restrict the pressure of that gas simply as a side effect of stuffing less gas into a given space. Pretty basic, right?
With that out of the way, I don't see why a self-regulating adjustable gas block/system could not be constructed (I'll freely admit that this is where my lack of knowledge will really be apparent). I am envisioning a design with two, sequential gas ports; the first being used to push against a spring loaded valve that restricts the passage between the second gas port (which would actually provide the gas to operate the rifle) and the rest of the operating system. Conceptually, this valve would, at atmospheric pressure, leave that passage wide open, thus providing no restriction to gas flow between the second gas port and the rest of the operating system. As barrel pressure increased, the valve would push harder against its pre-load spring and close off more of the passage between the second gas port and the rest of the rifle operating system. The self regulation function is evident at this point... the less gas pressure there is in the barrel, the less gas pressure there is to "choke" the passage between the second gas port and the rest of the gas system, and the greater the gas pressure in the barrel, the greater the effect on the spring loaded valve and therefore the greater the "choke" on the gas passage.
I'm certain that I'm not innovative in this thinking... there are enough people who have a hell of a lot more knowledge/skills than I do, and such a system does not exist today (that I am aware of). I can therefore only conclude that there has to be something that I am overlooking; do any of you know what that might be?
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