How the AR system is not Direct Impingement

[worddoer]

For years the AR system has been incorrectly described as direct impingement. In actuality, the AR system uses a bolt carrier based piston instead of a gas block based piston....but it does use a piston.

I thought that many would find this video quite interesting.

[video=youtube;4xlKgkwt6Ro]https://www.youtube.com/watch?v=4xlKgkwt6Ro&list=WL[/video]

 

[Wanderer]

I enjoy Ian's work as much as the next guy, but I don't really agree with the idea that the Stoner system definitively *not* DI in any way. I think of it as a sort of hybrid system; yes, the bolt does act as a piston of sorts, but the vented gas does also directly impinge on the bolt carrier itself (the circular "shelf" that forms the other end of the expansion chamber) and pushes it back to unlock the bolt. Chris Bartocci of Small Arms Solutions likes to use the term "internal piston" to differentiate it from more traditional "external" (that is, external to the bolt carrier) piston systems, which I believe it is a pretty good way to think about it. But I still think it's not technically incorrect to also describe it as DI, or at least as having DI elements.

 

[russc2542]

As a talking point, what would truly be direct impingement then? (and because I'm curious from an engineering/tech side). Wouldn't anything gas operated need a sealed chamber for the pressure to act on which would technically be a piston? As such, lacking a MORE direct impingement model, I would accept having the piston within the bolt carrier and operating differently (pushing the bolt and bolt carrier apart vs pushing back on the bolt carrier from the gas housing as most piston designs) be called internal piston or DI interchangeably. let me bust out MS paint to elaborate...



I will grant that the nomenclature isn't technically accurate but how do you make use of the pressure without some kind of a pressure containment system?

 

[worddoer]

As a talking point, what would truly be direct impingement then? (and because I'm curious from an engineering/tech side). Wouldn't anything gas operated need a sealed chamber for the pressure to act on which would technically be a piston? As such, lacking a MORE direct impingement model, I would accept having the piston within the bolt carrier and operating differently (pushing the bolt and bolt carrier apart vs pushing back on the bolt carrier from the gas housing as most piston designs) be called internal piston or DI interchangeably. let me bust out MS paint to elaborate...

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I will grant that the nomenclature isn't technically accurate but how do you make use of the pressure without some kind of a pressure containment system?

Look up Ian' s videos on the MAS49. That is a true direct impingment gun.

 

[cosermann]

In any system, the gas is directly impinging on something.

 

[russc2542]

Look up Ian' s videos on the MAS49. That is a true direct impingment gun.

OK, I'll buy that.

Swedish Ljungman / AG M/42 as well. Looks to basically be the same idea as the MAS

In any system, the gas is directly impinging on something.

Oh but there are semantics to debate! This is the internet after all. lol

 

[Bfish]

In any system, the gas is directly impinging on something.

This is exactly what I was about to say

 

[snorko]

MAC did a very good video on this question as well.