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Thread: Stoner AR Operating System Technical Detail

  1. #51
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    Quote Originally Posted by LRRPF52 View Post
    The really important step that the Ljungman gave us was that it got rid of a failure-prone op-rod or piston. It was a major leap in self-loading firearms technology, getting away from the op rod breakage and bending seen on the 1920's designs, which plagued the SVT-38/40, and the Garand. Army Ordnance didn't learn much from those lessons, and coughed up the T44/M14 abortion, while forward thinking minds looked elsewhere. It should be no surprise that the AR15 beat the hand-selected M14's in the Fort Benning trials in both accuracy and reliability.

    You can really call the Ljungman Direct Impingement system pistonless.

    The Stoner system re-introduced the piston by blending it with the bolt tail and making it stationary when locked. This is the critical distinction between the two, which is why it uses internal gas expansion to operate the system. It wasn't a way to game the patent system over the Ljungman, but an unexpected evolutionary and significant improvement over Direct Impingement, by reintroducing the piston in a way that solved the problems with earlier piston guns, while capitalizing on the advances of the Ljungamn's elimination of the op-rod.
    Again, the definition of a piston is something that's acted upon by fluid pressure. By necessity it's a moving part. Furthermore, it then actuates other moving parts. The bolt in an AR isn't acted upon by the gas (the carrier is), and it doesn't actuate anything (it is itself actuated by the carrier). All the bolt tail does is serve as a gas plug. If you want to call anything in an AR a piston, then it has to be the carrier. It works identically to a female piston at the end of an op rod.

  2. #52
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    A couple corrections.

    Quote Originally Posted by BGREID View Post
    The bolt does have piston rings on it.
    The bolt design incorporates gas rings, not piston rings. "Piston rings" would lead a person the the incorrect logic that the bolt is a piston because it has seal rings.

    Quote Originally Posted by HansTheHobbit View Post
    Yes, a piston has to move to be a piston.
    Not necessarily, as a piston is only the inner fitting of a sealed chamber, where the cylinder is the outer fitting. However, it wouldn't be reasonable to use this to conclude the AR is a piston operated weapon, as the presence of one piston in an entire system does not dictate the entire system is a piston operated system.

    A couple observations.
    Impingement. To impinge is to directly strike, dash or collide with. This would imply the process of channeling gas into a chamber which is forced open by a rapidly increasing volume of gas cannot fit the definition of Direct Impingement, because there is no impingement.

    This still doesn't show us that the AR design is piston operated.

    More at 11.
    Nobody ever got shot climbing over the wall into East Berlin.

    Delivering the most precision possible, at the greatest distance possible, with the highest rate of fire possible.

  3. #53
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    Quote Originally Posted by Leuthas View Post
    A couple corrections.


    The bolt design incorporates gas rings, not piston rings. "Piston rings" would lead a person the the incorrect logic that the bolt is a piston because it has seal rings.


    Not necessarily, as a piston is only the inner fitting of a sealed chamber, where the cylinder is the outer fitting. However, it wouldn't be reasonable to use this to conclude the AR is a piston operated weapon, as the presence of one piston in an entire system does not dictate the entire system is a piston operated system.

    A couple observations.
    Impingement. To impinge is to directly strike, dash or collide with. This would imply the process of channeling gas into a chamber which is forced open by a rapidly increasing volume of gas cannot fit the definition of Direct Impingement, because there is no impingement.

    This still doesn't show us that the AR design is piston operated.

    More at 11.
    The gas does indeed directly collide with the BCG, specifically the gas rings you mention, after it is routed through the carrier key and into the carrier itself. The system is not driven by the bolt carrier assembly, it is driven by the gases that impinge upon the bolt carrier assembly, which then move the carrier rearward, unlocking the bolt from the barrel extension via the can pin.

  4. #54
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    Quote Originally Posted by HansTheHobbit View Post
    Again, the definition of a piston is something that's acted upon by fluid pressure. By necessity it's a moving part. Furthermore, it then actuates other moving parts. The bolt in an AR isn't acted upon by the gas (the carrier is), and it doesn't actuate anything (it is itself actuated by the carrier). All the bolt tail does is serve as a gas plug. If you want to call anything in an AR a piston, then it has to be the carrier. It works identically to a female piston at the end of an op rod.
    This was already explained in great detail to you here in the thread. The Stoner bolt tail is a static piston, and does in fact act on the carrier by sealing the chamber with the gas rings, causing the gas to expand in the chamber.

    Think of it as a piston that throws the housing, like the syringe example. From the patent of one of the greatest firearms engineers in history again:

    It is a principal object of this invention to utilize the basic parts of an automatic rifle mechanism such as the bolt and bolt carrier to perform a double function. This double function consists of the bolts primary function to lock the breach against the pressure of firing, and secondarily, to act as a stationary piston to actuate the automatic rifle mechanism.
    Doubling down on the idea that the Stoner system does not have a piston is in direct contrast to what the patent states, and what the bolt actually does in reality. It is a stationary piston. The Ljungman Direct Impingement has no piston at all. This is why the AR15 is not DI, and the Ljungman is. If this were a court case, it would be very easy for me to win a ruling by simply reading the patent aloud.

    Stoner and his aerospace engineering team at ArmaLite were not ignoramuses, and they had over a dozen previous firearms designs alone in house they had worked on, many of which are still in use today. (AR-7, AR-10, AR-18...)

    If this is simply a personal issue where one feels a need to double down on the incorrect definition we were all plagued with before we could read the patent (guilty myself), then I understand, but digging in one's heels on this isn't going to help any. The only real solution is to admit being wrong, move forward, and accept what is said in the patents.

    When I first heard the Stoner system wasn't DI, I was ready to jump down someone's throat and correct them, but then I noticed this little link to the patents, which I took the time to read and then realized we had been calling this the wrong thing all these years. A lazy person who looked at the Ljungman probably associated the AR10/15 with it, then said, "It's like the Ag m/42 Ljungman direct impingement system." And gun people called it that ever since.

    We were simply wrong.
    Last edited by LRRPF52; 10-22-15 at 12:43.

  5. #55
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    Well, lookie here what I found. Someone was wearing his thinking cap that day.

    DIcomparison (1).JPG

    Just because something looks like a piston doesn't mean it is one, even if it has gas rings. For example, I could easily put some gas rings on the end of the Ljungman's gas tube, but that WOULD NOT make it a piston. Again, a piston is impinged by gas, and it actuates other moving parts. The bolt in the AR does neither of these things.

  6. #56
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    That diagram misses the main point of internal expansion. The gas expands in all directions with containment in the Stoner system. It does no such thing in the Ljungman.

    It takes a practical understanding of applied physics to get this. Some people are capable of understanding it, while others either can't or refuse to. The bolt in the Ljungman does not contain or direct any gas. It simply contains the pressure of the chamber, then articulates in the carrier.

    In the Stoner system, the bolt performs several functions, one of which is the piston.

  7. #57
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    Quote Originally Posted by LRRPF52 View Post
    This was already explained in great detail to you here in the thread. The Stoner bolt tail is a static piston, and does in fact act on the carrier by sealing the chamber with the gas rings, causing the gas to expand in the chamber.

    Think of it as a piston that throws the housing, like the syringe example. From the patent of one of the greatest firearms engineers in history again:



    Doubling down on the idea that the Stoner system does not have a piston is in direct contrast to what the patent states, and what the bolt actually does in reality. It is a stationary piston. The Ljungman Direct Impingement has no piston at all. This is why the AR15 is not DI, and the Ljungman is. If this were a court case, it would be very easy for me to win a ruling by simply reading the patent aloud.

    Stoner and his aerospace engineering team at ArmaLite were not ignoramuses, and they had over a dozen previous firearms designs alone in house they had worked on, many of which are still in use today. (AR-7, AR-10, AR-18...)

    If this is simply a personal issue where one feels a need to double down on the incorrect definition we were all plagued with before we could read the patent (guilty myself), then I understand, but digging in one's heels on this isn't going to help any. The only real solution is to admit being wrong, move forward, and accept what is said in the patents.

    When I first heard the Stoner system wasn't DI, I was ready to jump down someone's throat and correct them, but then I noticed this little link to the patents, which I took the time to read and then realized we had been calling this the wrong thing all these years. A lazy person who looked at the Ljungman probably associated the AR10/15 with it, then said, "It's like the Ag m/42 Ljungman direct impingement system." And gun people called it that ever since.

    We were simply wrong.
    Okay, if we want to go getting all super technical, then the syringe example is complete nonsense. Syringes don't have pistons, they have plungers. And the bolt DOES NOT "throw the housing." The gas pressing on the back of the carrier causes it to move (impinges upon it rather), thereby unlocking the bolt. All the bolt does is seal the pocket.

    The fact of the matter, though, is that it doesn't make any difference even if the bolt is a piston. Because the definition of DI is when the gas is routed directly to the carrier without an intermediary. The AR meets that criteria, so it's DI by every interpretation of the standard definition. If you want to say that the AR isn't DI then you have to change the definition of DI. Which would be tricky.

  8. #58
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    Quote Originally Posted by LRRPF52 View Post
    This was already explained in great detail to you here in the thread. The Stoner bolt tail is a static piston, and does in fact act on the carrier by sealing the chamber with the gas rings, causing the gas to expand in the chamber.

    Think of it as a piston that throws the housing, like the syringe example. From the patent of one of the greatest firearms engineers in history again:



    Doubling down on the idea that the Stoner system does not have a piston is in direct contrast to what the patent states, and what the bolt actually does in reality. It is a stationary piston. The Ljungman Direct Impingement has no piston at all. This is why the AR15 is not DI, and the Ljungman is. If this were a court case, it would be very easy for me to win a ruling by simply reading the patent aloud.

    Stoner and his aerospace engineering team at ArmaLite were not ignoramuses, and they had over a dozen previous firearms designs alone in house they had worked on, many of which are still in use today. (AR-7, AR-10, AR-18...)

    If this is simply a personal issue where one feels a need to double down on the incorrect definition we were all plagued with before we could read the patent (guilty myself), then I understand, but digging in one's heels on this isn't going to help any. The only real solution is to admit being wrong, move forward, and accept what is said in the patents.

    When I first heard the Stoner system wasn't DI, I was ready to jump down someone's throat and correct them, but then I noticed this little link to the patents, which I took the time to read and then realized we had been calling this the wrong thing all these years. A lazy person who looked at the Ljungman probably associated the AR10/15 with it, then said, "It's like the Ag m/42 Ljungman direct impingement system." And gun people called it that ever since.

    We were simply wrong.
    The bolt does NOT act on the carrier. It allows the gas to act on the carrier. The bolt is stationary, as stated in the patent, and by your own admission. A stationary object by definition does not act without a force compelling it to do so. That is Newton's very first law of physics:
    https://en.wikipedia.org/wiki/Newton%27s_laws_of_motion

    If there is a piston, it is the female counterpart to the bolt; the carrier. The carrier could even be considered the male piston, inside the upper receiver. Yes, the AR15 design has parts which can be considered or labeled pistons. But it is not a piston operated system, as we know it (long or short stroke).

    Aside from the patent, the ACCEPTED usage of the terms DI and Piston Operated refer to a traditional AR15 with a gas tube as designed by Stoner, and guns with op rods like the AK47, respectively.

    The nonsense of trying to reclassify one or the other has no purpose other than to create confusion of decades old, established nomenclature. If Stoner were alive today, we could certainly ask him which he would prefer. But since he's not, all we have are the terms we've used to differentiate guns that use gas tubes and guns that use op rods. I think Stoner would have liked to keep his rifle as far from designs like the AK47 as possible, and would prefer that his design be called DI. However, maybe he would have used a term like Direct Expanding Gas system. In any case, history has spoken and the terms are well in use and accepted by the vast majority of well informed industry professionals and end users alike. These discussions are purely academic and will have absolutely no effect on what terms are ubiquitous when used to describe Stoner's gas system.

    Just because the bolt is labeled a piston in the patent does not mean that the bolt is what drives the system. The bolt is imparted forces DIRECTLY from the gases being vented from the gas tube. The patent states the system is not a CONVENTIONAL impingement system. It does not state it is NOT an impingement system.

    Just like our laws state what is illegal, by default, anything not illegal is legal. I don't think your case is as cut and dry as you represent it to be

  9. #59
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    Quote Originally Posted by LRRPF52 View Post
    That diagram misses the main point of internal expansion. The gas expands in all directions with containment in the Stoner system. It does no such thing in the Ljungman.

    It takes a practical understanding of applied physics to get this. Some people are capable of understanding it, while others either can't or refuse to. The bolt in the Ljungman does not contain or direct any gas. It simply contains the pressure of the chamber, then articulates in the carrier.

    In the Stoner system, the bolt performs several functions, one of which is the piston.
    Your statement contradicts itself. Pressure is a force imparted by gas, fluid, or mass.

    pressure
    [presh-er]
    Spell Syllables
    Examples Word Origin
    noun
    1.
    the exertion of force upon a surface by an object, fluid, etc., in contact with it:
    the pressure of earth against a wall.
    2.
    Physics. force per unit area. Symbol: P.
    Compare stress (def 6).

  10. #60
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    Can someone please identify the piston in this system?

    di piston.jpg

    Sry, I don't know why the thumbnails are there. I tried to make them go away, and they multiplied. Just ignore them.
    Attached Images Attached Images
    Last edited by HansTheHobbit; 10-22-15 at 13:32.

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