Smyth Busters: The AR-15, Direct Impingement or Piston Operated?
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- Опубликовано: 17 окт 2024
- Today, Brownells Gun Techs™ Steve Ostrem and @CalebSavant want to settle a debate. Or maybe just stir the pot. The debate among AR-15 fans is that the AR-15 platform actually DOES NOT have a direct impingement operating system. Steve asks the pertinent question: So where's the piston then? Caleb gets technical and starts by defining terms.
A traditional GAS PISTON operating system - like on the AK series, FN FAL, HK416, or BRN-4 - sends combustion gas through a gas port in the barrel into a sleeve that applies pressure on a piston that pushes on the carrier to unlock the bolt. In a DIRECT IMPINGEMENT operating system, instead of the gas pushing on a piston, it goes down a gas tube and pushes directly on the carrier to cycle it.
The AR-15 works a little differently. The gas goes THROUGH the carrier and pushes directly on the BOLT to move it. The carrier has two holes that vent the gas out of the carrier and out the ejection port. This helps minimize muzzle rise, which can be quite pronounced on a pure direct impingement system. But the big news is that the bolt acts like a piston and the carrier acts like the sleeve. So the AR-15's operating system really IS a lot like a traditional piston system!
Pure direct impingement rifles like the old Swedish AG42 or French MAS-49 get a lot of carbon fouling on the carrier because the gas doesn't get vented out like it does on the AR-15. The AR-15's bolt and carrier still get dirtier than those of a traditional piston-operated rifle, which keeps all the gas (and all the fouling) up front in the gas block.
So the "myth" is not busted. The AR-15 actually is not a true direct impingement rifle because the bolt itself acts as the piston and the carrier acts as the sleeve.
Merry Christmas everyone! I gotta give a shoutout to Rad Labs 3d for the sweet custom Brownells AR stand. Oh, and if you haven't yet, go watch Violent Night the movie.
When are we getting the sexy christmas calender
I want a cut in half AR
I’ll second the calendar request. I wanna see kaleb all cute as Mr February
Internal piston doesn't sound catchy. We have short stroke and long stroke, why not call is the Stoner Stroke Piston (LP, SP, SSP for dem acronyms)?
@@PAIsIllegal probably not one worth owning honestly. A barrel is not something you want to cheap out on. There are affordable barrels that are good but I would stay away from hunting "dirt cheap" when it comes to key components in general.
Stoner was a freaking genius. The AR is basically a tube gun, no reciprocal mass that is of the bore axis except for the tiny hollow gas key.
What do you mean? The bolt is reciprocating.
@@freeandcriticalthinker4431 I think he meant to say that all the reciprocal mass is inline with the bore. Other than the gas key.
*OFF the bore axis
@@freeandcriticalthinker4431 I think he meant to type, "no reciprocal mass that is ABOVE the bore axis except for the tiny hollow gas key."
Being "above the bore axis" is the KEY thing. Hah, pun!
67
Kalashnikov was more genius.
I like how Steve tries to play the dummy role, while we all know he's very intelligent.
if anything he has probably known this all of his working life.
I like how he just gives that ho-hum look and takes another drink of coffee ☕️.
I think the gray haired guy hits that coffee cup a little too much. This video should be used for a drinking game.
@silent1967 After they stop the video shoot, that coffee swilling guy has to take a serious piss
@@jetboy770371 Don't worry, when you get as old as he is you'll be pissing a lot too, whether you drink coffee or not.
A couple years ago, I heard Chris from Small Arms Solutions refer to it as an "internal piston" system. At first, it went against everything I had been taught about the system since I was issued my first M16A1 in the early 80's. Then he explained it much the way Caleb did, then the light bulb clicked on. I've referred to it as internal piston operated ever since. If I'm not mistaken, I believe there is old interview with Mr. Stoner where he calls it internal piston also. But I'm not 100% sure on that. Great video guys, as always!
Pistons are contained by cylinders. They are always internal. You had it right the first time. The entire bolt-is-a-piston story came from the patent attorneys and their creative writing - not Stoner. Ever heard of the cylinder being driven and the piston being dragged along? No. No you have not, except for the AR fiction
@@Ni999 Have you ever driven a SuperMoto?
@@woodrowcall3158 No and not all supermotos use rotary engines. See my other reply. The AR bolt is still not a piston.
So, it's an internal piston system???
@@Ni999 So it is a cup piston, much like the LWRCI piston only the carrier is the cup piston..
"AR-15, Direct Impingement or Piston Operated?"
AR-15: "Yes"
You guys explain everything so well that even a novice can understand completely.
That is the real genius of these videos.
It’s a piston gun disguised as a direct impingement gun, lol
Great vid. Would love a part two about cost differences, reliability of gas piston and more parts to break, weight and recoil differences as well.
See the Adams Arms video. DI vs there piston upper. The DI upper is dirty as hell and runs hotter!
That's some great AR education, many thanks
"Oh hey Steve, didn't see ya there." It's the little goofy things I love about these videos.
When Caleb's pomade was made, Eugene Stoner was still sketching the AR design...🙃
I sometimes refer to rifles like the AR-15 and the Daewoo K1 as being "internal piston" rifles, as opposed to "external piston" systems like the AK-47 or the HK-416.
According to Eugene Stoner: the bolt is the piston.
"I'm not here to end it" and "that's a lot of syllables" totally got me. Lol. Good stuff.
Definitely a very elegant solution, seems like there's always something new to learn about the AR platform
I love these guys. The dynamic duo of Guntube.
DI has some advantages like self-cleaning of debris too.
THANK YOU!! I have been hearing people argue this point back and forth for YEARS, but none of them have been able to actually explain what direct impingement OR piston driven even MEANS. And since I didn't know myself, all I could do was smile and nod. Glad someone finally came along to explain it and put this shit to bed.
And this is where you get adjustable gas bolt carriers as well. Though, there aren't many of them.
I would agree that the AR is technically a piston system.
Just when I was finally understanding the difference between a direct blowback v. gas-recoil operated pistol (And at an elementary level at that) Steve and Caleb drop this one on all viewers! Good, interesting video (as always from the Smyth Busters duo), but I’m sure I’m not the only viewer still not certain I could explain the differences between the two operating systems, even after viewing.
It literally just comes down to where the gas is being introduced into the mechanism. At the chamber, at the gas key, at the piston face, at the bolt face, etc. The gas tube on an AR-15 is just a tube that dumps the gas into the receiver, that's it.
@@tedhodge4830 : TY Mr. Hodge. Happy Holidays.
Great videos. Not only informative, but entertaining.
Great deep dive into the DI gas system. One could argue, a lot of the heat is dissipated over the entirety of the DI gas system, vs all heat collected at the gas piston, forward barrel? Both systems have their pluses and minuses.
Okay, there are legit advantages for the Stoner system, but this is some extreme copium.
Keeping all the gas and fouling concentrated in one area makes cleaning much easier.
@@WaterZer0 Maybe, but all the heat, and weight, IS concentrated near the muzzle. That's not to MY liking. Your mileage may vary!
@@03redrubi I understand the weight issue, but where else would you want the heat?
@@WaterZer0 Not where my accessories, and hand are.
Who knew that Steve is a fan of Pitch Meetings? Super Easy, barely an inconvenience!
So much fun watching you guys, smart and informative!
I want to be able to like the Steve and Caleb videos more than once.
How did you guys know I was arguing with my brother about this on christmas?!
I'm late but wanted to drop by and say merry christmas and happy new year to Steve, Caleb and the Brownells crew!
PS. My dad already had Die Hard on when I arrived for our Christmas dinner..
from NH, Live free or Die!
Live free or die needs updating, I want to live free and live.
I propose the following change.
Live free or die fighting.
&
Give me liberty or give me death needs updating as well.
I have Liberty, death can wait.
@@ellerybice3787 The sentiment is there, it reads a little harsh out of context but I like the truth behind it.
I wish NH would bring in the Gadsden license plates like Virginia, the old man on the mountain is, well, old. Lol
Fueling an online gun argument? Classic Caleb moment.
Great video BTW
Hard to argue with facts. Great video guys.
"This invention is a true expanding gas system instead of the conventional impinging gas system." - direct gas, expansion, bleed off system
It is a piston, as described in Stoner's patent..
@@hairydogstail I didn't say it wasn't. Just pointed out that it isn't an impingement system.
``Your bolt acts as the piston...''. That is THE difference between the AR-15 platform and a piston driven platform like an AK.
As I already knew. Once you understand what direct impingement really means, and see how th AR works, it's self evident.
Great teaching. Thank you.
I've heard this described several times before and this is a good description with visual aids. Thanks guys much appreciated.
Merry Christmas to my favorite firearms duo🎄🌟
He really needs to take a sip from his cup during an eight minute video? What are you a child, need a sippy cup? Maybe take a bathroom break too. But excellent and informative video.
As a motorcycle technician, I think I know a piston when I see one. 😂
Is there any argumnet that direct impingement on an ar saves bolt to lug wear compared to piston?
It definitely does. I've shot both styles, factory and ones I've assembled, on various lowers, and even with a tuned gas system the short stroke gas piston uppers beat up bolt lugs. I've run factory Sig 516s and after market Adams Arms, different adjustments to the gas block different SpringCo buffer springs different buffer weights, etc, always saw a difference. Best thing I ever did to any AR was convert to the Vltor A5 buffer system and switch to an adjustable gas block. But even then they're different beasts. Having forward pressure on the bolt before the whole thing cams over definitely decreases wear on the rear of the lugs. But on 5.56 ARs I always change bolts at 5k rounds and on 6.5 Grendel or others I change bolts when I change barrels, whether 2k, 3k or 5k
@@DanielReyes-hz1qk thanks!
Do the vent holes cause any problems for left handed shooter? Such as blowing gas and brass in the face?
Now I'm wondering if I have a homemade icecream churn or a homemade icecream bucket !
It's pretty cool to see and hear it clearly explained 👍
With that better understood by me, I now get to wondering if Ruger's Mini-14 is actually best described as a direct impingement system gun? 🤔
Videos like this bring out the comments that prove society does not care to know proper language and the definition of words.
How much of a problem would you say carrier tilt is for gas piston systems? E.g. on the hk416.
Works like a steam engine in a locomotive or paddle boat invented in the early 1800s.
A roller locker is dirtier than a MAS 49 or 49/56.
Loved this episode. This is actually a topic of many a heated debate as I've tried to explain that the AR platform is both 'a little bit' piston, and 'a little bit' direct impingement.
It is nothing direct impingement
Internal piston via gas impingement?
@@michaelhill6451 Except, the means in which the AR15 cycles is the very definition of DI. The only piston action is merely to unlock the bolt by pushing it forward. Some of the gas is vented off, but much of it is used to push the bcg rearward. This is why you get gas blown out of the gaps in the rear of the receiver near the charging handle. Using an earlier prototype that never made it into production and doesn't represent the final design as an example doesn't work, my friend.
@@michaelhill6451 And the debate continues. I guess I'll have to do some reading!
@@waruikoneko1635 you are not understanding the physics and saying Eugene didn't know better than you on his own design????? You got a wall of participation trophies, don't you.
Great video. I think that we can lose our minds delving into the absolute best term for everything. Back when I was in Army as an 18B we were taught that there were 2 types of gas piston systems (gas piston & gas tappet) now it’s normally referred to as long stroke gas piston and short stroke gas piston, which in my opinion makes less sense but it is what it is. As long as someone that should be in the know doesn’t call a “magazine” a “clip” or a “cartridge” a “bullet” I’m good, and there are plenty of high profile gun YT channels that use the term bullet when referring to a cartridge.
As long as it works when you need it to, call it what you want. Happy holidays gentlemen.
Not only is it a piston gun, it's a long stroke piston since the piston travels the entire distance with the carrier
Why would you say that?! 😂
@@dieudonnesaive6603 Re-read what he wrote..
@@dieudonnesaive6603 Because it kind of is technically true, it's just missing the operating rod lol
@@Alex-12381 technically since the bolt isn’t fixed to the bolt carrier, I’m not sure it’s exactly true? The piston (bolt) is its own moving part aside from the carrier. It really just depends on what definition of “long stroke” we roll with. There’s a hundred different ones out there, all of them kinda flawed in one way or another.
ARRRGGGGG - and I had to get on Brownell's BRN-4 wait list
Thank you very much for this and all the other explanations. The info you guys provide really helps me understand the workings of my firearms. And the differences between many that seem very similar.
Why is this debated. Its literally called a piston system in the bloody patents.
Eugene Stoner was an Aerospace Engineer by trade. You can't have unbalanced forces on aircraft and expect them to fly well. He felt the same way about firearms. He wanted all action/reaction forces to be on the bore axis. I've seen slow motion video's of AK's being shot and you can see the barrel flex down slightly as the piston is pushed out of the cylinder about an inch above the bore axis.
Stoner was never an engineer..He never went to college..
Ak vs Ar = apple's vs orange's
It's an old and boring conversation
Rofl Steve 😂 “I just learned how to pronounce direct impingement”
Can you do a segment on Canada's deadliest and most prolific .22 gauge fully semiautomatic assault rifle, the Buttmaster?
Steve had his cloaking ability activated at the beginning...sorry steve, didnt see you there! 🤣
Any good solutions for covering/protecting raw aluminum that's exposed, aluminum black? Anything else???
very good info guys. Thanks a lot.
Great information ,good comedy ( thx 4 all of the videos ) !
Three fun facts for everyone:
1) Everyone wants to be right all of the time.
2) Many people are stupid, but none of them realize it.
3) A P320 will not fire without the trigger moving rearward.
You could argue that in the MAS and the AG-42, the bolt carrier is the piston, though rapped around the gas tube, rather than being inside the sleeve of the gasblock. So a "long stroke bolt carrier integrated spigot gas piston", while the AR-15 is a "short stroke bolt integrated gas piston".
Great Video! I have both (DI"ish" and Piston).. I love both for different reasons. Piston definitely handles suppressors much better, and can operate even if fully submerged in water. My DI rifles are great as well, lighter recoil, flip is manageable with a muzzle brake. Both are great designs.
Well here's the problem heckler & Koch are charging the United States Marine corps $1700 for each M27 IAR which is a 416 based rifle
The Army is acquiring M14A1s for $700 to $800 a piece
It seems to me that it's a lot better to tell a soldier who is already disciplined to run a cleaning rod down through an M4 as opposed to handing out $1700 just to have that Short stroke piston
It requires a little bit extra maintenance but the AR-15 direct gas impingement or internal piston depending on how you want to split things works perfectly for the United States military we've never had any major problems with it nobody has gotten killed because the gas system itself let's keep what works and not hand out almost $2,000 for a 416.
Great video! Also, love the Ryan George mug Steve's got there.
Internal piston system to be specific
Those two holes are perfect for dropping oil in to get your gun back up and running.
They are also perfect for blowing out ingress that shuts down external piston rifles..
Who am I to disagree? I work at a Gun Range and am always learning from our Gunsmith, so I am not going to argue any points concerning operating systems, etc., but will be watching and learning what I can from you guys (Steve and Caleb). Thanks again for another great video.
Steve forgot to put his hip waders on for the level of BS Caleb was ready to sling on this topic… 😂
One important point: Eugene Stoner’s genius in designing that gas chamber inside the bolt carrier does something VERY important. The bolt is pushed *forward* while the bolt carrier is pushed backward. This relieves pressure on the bolt lugs, making it easier to disengage from the matching barrel extension lugs and reducing wear and tear.
It gives the gas a chamber to expand into that allows it to impart force to the carrier, allowing it to move. The delay caused by the carrier moving and the bolt staying locked allows the chamber pressure to drop sufficiently, relieving pressure on the locking lugs. The lugs want pressure pushing them into the lugs on the extension, that's why they're called locking lugs.
@@ShortArmOfGod I do not understand what point you are trying to make.
Interesting view! But the technical operation never lies…
Whats the Difference/advantage between a long stroke Piston and a short Stroke piston? A HK416 vs PWS share many of the same features. PWS has an attached piston rod the HK does not. Is there a reason on vs other is better wear/tear, Accuaracy, harmonics... I would like to see a deep dive on pistons and the conversions kits.
I would like to know if the Wolf short stroke gas piston 556 upper is a copy of the HK or SIG short stroke uppers . Do you know?
Hi Love your videos. Would you think about discussing the Noreen gas system they use on their AR style 30-06 and 338 models??
Good explanation. It would have been even clearer if you had a true direct impingement gun to show side-by-side (like you mentioned - the MAS 49/56 or the AG42/Hakeem/Rashid)
It’s actually a internal piston driven system that we somehow started calling direct impingement
Direct impingement is this damn shoulder problem my surgeon hasn’t been able to fix since 2019😡
I can almost hear the ARFCOM users angrily typing right now…
I hope you respond because I am curious if I would be correct in saying it is a gas impingement piston system.?.?.?
As long as it works, that’s all I care about
So, the HK is a short-stroke piston and other AR-15's are "bolt piston" operated?
Internal expansion system, as described on the Stoner patent.
Nomenclature has accepted the terms for simplicity of differentiating the types of piston or "gas guns".
IDI...
Improved Direct Impingement
The gas is still directly impinging (impinging: the act or fact of striking or touching something, or the effect produced by this) upon the bolt carrier group. It is just doing so in a way that is greatly improved over the methods of direct impingement utilized by previous designs.
Both of you are real geniuses
Nice theory....
But mechanically speaking,
it's just an expansion chamber, instead of a pistons.
no because it reciprocates according to the gas pressure which is a piston
@@AR15andGOD nope, it's as an expansion chamber, not a piston, just to unlock the bolt. An "apparent piston".
The long stroke piston system is closer to direct impingement than the AR15 technically speaking.
I've always thought of the AR as a piston system. Gas rings on the bolt/piston.
Maybe a direct impiston system? I just made that up, lol
Seriously though, you are correct and gave the best explanation to date.
Unless your running a non-transferable FA AR, have Joe’s $1.7T budget for ammo, and shoot everyday, a “direct impingement” system will serve you very well. The piston gun is cool and all, but as we add accessories to the platform, you’re better off loosing weight where you can, and carry more ammo - never run black on ammo! Also, as you age not so well like this ole retired combat gruntpa (ABN), you tend to gravitate to lighter systems, lol.
Interesting knowledge right here, thank you gentlemen!!
It seems like semantics though bolt has rings ( like a piston) but it seems like 2 actions or that the bolt is locking and unlocking while the bolt carrier blows back
Wouldn’t the new sig mcm spear then be direct impingement? It doesn’t have that gas key. It has a small gas tube which hits directly on the bolt carrier which moves and unlocks the bolt.
Can you measure, slow mo, the difference between di vs piston gas blowback gasses
I would call it direct impingement because the gas is still interfacing with the bolt carrier in the action of the firearm, where with what is conventionally referred to as a short or long stroke piston the exchange happens outside of the action of the firearm. But I can see both sides.
What I’ve been wondering is if in some similar manor with different methodology, how different is this Direct Impingement design from a direct blowback system on a smaller firearm.
I haven’t really studied Direct blowback all that much but from what I understand it seems as if bolt mass and recoil spring tension keep the bolt closed tight enough allowing for the force of the bullet being expelled to cause the next round of a direct blowback firearm to cycle as the bolt travels back and the spent casing is ejected from the firearm. In some ways, I’m seeing a lot of similarities with the Direct Impingement system and how the system uses the gas of the round itself to cycle the next round. Idk if there are any similarities at all but I thought it was a surprising analysis.
Awesome Sirs!!
Justaquestion...
Since gas compresses...is the shorter amount of time the gas is in the piston gas block relate to a quicker reaction time of the bolt...?
Does the compression of the gas in the tube come into play with the timing of the operation...?
The AR gas system is tightly balanced and timed. It requires a set amount of gas energizing the gas tube and expansion chamber for a specific amount of time and specific pressure. You affect that by gas tube length, gas port size and dwell time. This is why you can't simply chop barrel length without making adjustments, else you start introducing timing errors.
So does the piston driven gun create better round velocity since less gas seemingly is sent back into the gun to operate the bolt??
You mean external piston driven guns??No..
Steve - you miss spoke just a little bit at around 4.58 in the video. As I understand it, the bolt is locked in against the chamber because of the lugs. So therefore the bolt doesn't go forward - the carrier gets pushed rearward from the gas.
For people who understand the gas system, we know what you meant. For people who are trying to understand the gas system, what you said might be confusing.
I enjoy you guys videos, so keep up putting them out. I've learned a lot from you guys and others like you.
John
The forces from the gas still expand in all directions including towards the bolt when it is in battery. The force from the gas expansion has to be overcome before the bolt can move rearwords, I think that's what they meant.
I should be call the "Stoner Operating System". I think he deserves that honor.
Is there a way to convert from DI to a long stroke piston system? Or do I need to swap the whole upper?
In the BRN4 then, Where does the gas go after triggering the piston? Does all the gas then simply follow the projectile out the muzzle? And is there more recoil to one system over the other?
It vents under the handguard.
Traditional piston systems generally have more mass in moving parts and it's off the bore axis -- therefore more recoil.
The brilliance of the AR is twofold:
- Keeping all the moving parts on the bore axis
- Generally lower mass of moving parts (really low in tuned competition rifles)
@@maxxon99 Thank you!
Which one takes away more from the muzzle velocity direct impingement or piston driven?
Depends on how big the barrel port is..The AK and M1 Garand needs a bigger port compared to a piston gun that uses gas rings like the FN scar or Aug..In any case the difference is insignificant..
Amazing. Genius stuff
Serbu BFG50A is also DI.