Why Gas Piston over Direct Impingement?

Discussion in 'Auto & Semi-Auto Discussion' started by urban, Oct 15, 2010.

  1. urban

    urban New Member

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    I'm very very green when it comes to ARs, M16s, AKs, ACRs, etc. So bear with me. I want to build an AR15 sometime in the beginning of next year (when finances allow), but it's lead to a very interesting debate I didn't know existed, why would you choose gas piston over a direct impingement system?

    I was reading about the Bushmaster ACR (and watching the future weapons episode) and noticed they went with a piston system, and then boasted that their rifle was half a pound lighter than it's M16 counterpart. If weight was such an issue wouldn't you go with DI instead?

    What advantage does a piston system have over DI? many of the people I know have said it's largely a solution to a problem that doesn't exist. Both systems require cleaning and regular maintenance, it's not like the piston system never gets fouled up. If you took care of your rifle like you're supposed to, is there ANY advantage? For people like me who will likely never see combat, nor spend weeks at a time firing off shots without cleaning my rifle, is there any good reason to go with a piston system?

    I'm just trying to wrap my head around why magpul would design the assault rifle of the future and then slap a piston on it. What am I not understanding?
     
  2. mrm14

    mrm14 Active Member

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    Because gas piton doesn't jam up form dirt and muck like gas impengimet does when it can really count. Yeah, you potentially sacrifice some accuracy but you get reliability in return.

    Just my 2 cents worth.
     

  3. TheDaggle

    TheDaggle Member

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    I'm just riffing here, but hear me out. Given the direction of gas flow, the only way for muck to get into your gas return system is to have it chambered in front of your round and fired through the gas tube, right? Well if there's so much dirt, sand, or mud on your bolt/in your mag/in your receiver that it clogs your gas tube, your rifle is probably going to fail as a result of your follower or bolt getting stuck anyway, regardless of which system funnels gas back to the debris-clogged receiver....
     
  4. Dillinger

    Dillinger New Member

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    This argument can go 'round and 'round for days, so I will try to take some of the steam out of it with this explanation, not saying I will be successful... LOL

    The Direct Impingement system is the way the platform was designed. It harnesses gas from the round and directly cycles the bolt/action.

    When the M-16 went to Vietnam, there were complaints that it would not work well if dirty/muddy.

    Changes were made, education was initiated and the weapon system moved forward.

    At the same time Good Ol Mikhail over in Mother Russia had developed the AK platform, which was a knock off/copy/ hommage to a German design.

    Ths system is a piston, or op rod, type platform. The gas is harnessed near the bore and it drives a piston to cycle the action. As there is less overall travel of gas, the "piston" or "op rod" covers the distance with solid metal and does not allow the same kind of dirt/mud/grime.

    Wars come and go, AK's come to the states, people start getting interested and then we have the AK vs. AR battles/tests/comparisons.

    Someone got the idea of why not combining what is great about the AK, the fact that it will run no matter where you are deployed, with the more familiar AR platform.

    There was money to be made - need I say more?

    From a very novice gunsmith wannabe standpoint, you get this:

    The AK is not as accurate as the AR - regardless of who made each model. If you compare skill level of maker to skill level of maker, the AR is more accurate. The piston system of the AK causes flex in the barrel with each follow up shot, so accuracy is compromised past shot one.

    Adding a "piston" to an AR does the same thing. It is "more reliable" but you are losing accuracy because of the way the cycling of the action must work, you have harmonics along the barrel.

    At street to street, house to house type of fights will this affect the "average" shooter?

    NO! Absolutely not. Out to 50 yards, Minute of Bad Guy is going to be Minute of Bad Guy unless you are trying for a head shot.

    At 200 or 300 yards?

    Yes! A hit with a DI AR might not be a hit with a piston AR. Not that you can't get man sized hits, you can, but the DI is going to be more accurate.

    So, you want to build one. The Piston versions are more expensive currently so if cost is a factor, and I guage that it is by your post, it is going to be cheaper to build a DI edition.

    Personally??

    I live in the Pacific Northwest. We get rain, wind and usually blowing pine needles and "junk" about 8 months out of the year. Now, I have never gone on a three day creep with my AR, or put a lanyard on it and pulled it through a swamp, followed by a sandbox, followed by a wet concrete pour, but I have never had weather conditions cause my weapon to stop working. :rolleyes:

    Could it happen? Yes. If you do not take care of your equipment, any piece of equipment can fail, for the most part.

    For most folks, the benefit of the AK has always been it will run dirty, cold, wet anywhere on the planet and keep heads down with that distinctive chatter.

    In my mind the benefit of the AK has always been the heavier round. Why take the negative, the piston/op rod, and keep the smaller, less powerful AR cartridge?

    I feel the Piston AR's are a solution where the problem was created by people Rube Goldberging something to death. :rolleyes:

    Good luck and feel free to PM if you have further questions on a build.

    JD
     
    Last edited: Oct 15, 2010
  5. russ

    russ New Member

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    As somebody who has one of each, I'm less dazzled by the piston setup now than I was before I had one. There's more felt recoil with a piston as well as whatever accuracy issues there may be. I was planning on my next build being another piston, but I'm slowly coming back to a DI setup instead.
     
  6. Highpower

    Highpower New Member

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    That says it all right there.

    In it's infancy, the M16 got it's (deservedly) bad reputation because of two reasons. The original ammunition was loaded with a particular ball type powder that left a lot of nasty gunk in the gas system and receiver that caused stoppages. The other problem was that troops were not even issued cleaning kits for these rifles in the beginning stages of Vietnam. :eek:

    After changing to a stick type powder which burned much more cleanly and issuing cleaning kits for the rifles, those issues went away for the most part. But the bad rep has lived on.....

    I've got a couple or three AR's and have shot the snot out of them. Have never had a stoppage or any problem with a crud buildup in any of them using the standard gas system. Granted, I don't drag them through mud and sand. If you plan on abusing a rifle, I'd go with a real AK. :D
    JMHO.
     
  7. masterPsmith

    masterPsmith New Member

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    I usually don't post much in the AR section, but having worked extensively with both types of gas systems in different platforms, here is the short of it.
    DI System in the AR imparts heat to the bolt carrier and bolt each time it is fires and under sustained fire, can get quite hot. It also vents the gasses into the reciever which causes undue fouling. If not properly maintained and lubed (you all know what proper lubing of an AR is, right?), "it will cause stoppages just when you need it the most".

    The Gas Piston system vents it's gasses outside of the reciever and imparts no heat to the bolt group. Other than the barrel getting hot under sustained fire, the reciever and bolt group stays cool to the touch and is not fouled by the powder gasses. Therefore the bolt and carrier requires less frequent lubrication and cleaning and the rifle will be more reliable.

    I have seen no real differences in accuracy in virtually identical rifles, using both systems.

    The inherent problems with the DI system will usually not affect the average shooter. Stoppages will, however, show-up in competitions with sustained fire and in extreme field conditions, or in rifles not maintained properly.

    Without a more detailed and lengthy write-up using many test results, photos, etc., that is the jist of it.

    Either system will serve you well.
    Hope this helps and heads off a long debate on the issue. I tried to make the compairison as simple as I could without being to lenghly.



    Jim.........................
     
    Last edited: Oct 16, 2010
  8. SecPro

    SecPro New Member

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    Can't add to much to this. At the end of the day bubba its all about your personal preference and financial status. For all intentive purposes, "they all kill the same." :)

    Why pay extra if you can get a bang stick to do the same job for less?
     
  9. urban

    urban New Member

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    Thanks for the help gentlemen. So it seems like a piston system is more appropriate to close combat where th accuracy issues are less relevant, when long periods between cleanin are more common, and drity environments and ammunition are present. But for civilian purposes there's no distinct advantage?

    I was thinking more about why the acr was made with a piston system and the guy on future weapons made it seem like its great advantage over the m16 was how easily it could convert to a non nato round for covert ops. If that's true, isn't it possible then that you're using ammunition made with the dirtier powder? If that's the case and you're working largely with battlefield pickups, then might a piston system make more sense?
     
  10. Dillinger

    Dillinger New Member

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    Huh?? You lost me there? :confused:

    If by "non-Nato round", you mean civilian ammo here in the states, I don't think it's an issue.

    How many rounds are you talking about putting down the barrel, honestly, without taking some time to clean the weapon?

    The reason I ask, and I am serious, is that we see guys come into the shop from Pierce County SWAT who train A LOT and they put TONS of rounds through their weapons on both full auto and semi auto fire. While they do take care of their weapons, frequently their weapons would not qualify as being of the "best" in care and maintanence. :cool:

    We see a weapon go 8,000-10,000 rounds and need a new gas tube and probably some rings. Perhaps a new recoil buffer spring here or there, but generally if a weapon comes in for a failure to cycle, there is a CLEAR reason when you take it apart and start looking into it.

    These are weapons that are shot frequently and with sustained fire.

    I just find it hard to believe that in a urban battlefield scenario a person is going to be shooting THAT MUCH without a time to let the weapon cool and to be able to clean it.

    You would probably end up dead from exhaustion and/or dehydration first.

    JD
     
  11. urban

    urban New Member

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    Guess i kinda lost my sense of practicality there for a second entertaining some crazed scenario where you're in combat and supplies have been cut off for long enough that failure from a dirty gun is an issue. Nevermind.
     
  12. Dillinger

    Dillinger New Member

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    Carry a couple of pipe cleaners and a small vial of this lube in your B.O.B. and you should be set for more battlefield time than you could ever hope to have to participate in. ;)

    Nothing wrong with thinking about extreme conditions and preparing for when the Space Zombies start walking the Earth, we all know they are coming. :eek:

    You are among like minded folks here. :p

    JD
     
  13. Jpyle

    Jpyle New Member

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    Plan on humping 10,000 rounds...you will run out of ammo in that scenario long before your gun seizes from firing. :)
     
  14. Zsnark

    Zsnark New Member

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    I like the AR overall better than the AK.

    Hi Gunners,

    Had one each copy of AR15 and AK47 (actually it was a Hungarian semi-auto: AK85S). They got more wear from cleaning than from hard use so I do not speak with any authority. Howsomever, in my non expert opinion, the AR handled better and was much more accurate than the AK. They were both fun to shoot. An analogy might be made as follows. The AR is a Corvette and the AK is SUV.

    I sold both of them when the Peoples' Republic of Kaliforniastan made it a pain to keep them legally. Sometimes I thought that at 50 yds. I could put a several 5.56 round through the same hole...I could not really, but it was accurate!

    Another thought is that I believe the direct impingement system is inherently lighter. Handling the Galil, in my distant memory, was a clunkier affair. I believe when the Israelis decided to build an ideal battle rifle they wedded the AK system to the 5.56 round. If I am not mistaken they actually use mostly M16s and market the Galils elsewhere. Also, H&K built a delayed blow back system piece in 5.56 which is also less handy than the AR.

    Dillinger, please correct me on the weight issue...sounds like you are more experienced than I am.

    Be well, and don't forget to Check Your Six;

    AAW
     
  15. KartoffelSalat

    KartoffelSalat New Member

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    i choose a piston out of ease of cleaning.....i seriously wish i had a nickle for every hour of liberty WASTED at the armory....scrapping baked on crap out of every little crevice of your bolt and bolt carrier not to mention the charging handle, the charging handle rail (especially around where the gas tube enters the upper) and having to illegally remove the trigger mechanism (apparently us grunts are too dumb to reassemble it) to get at the lowest point of the lower reciever ....MUUUCH easier to quickly clean a piston system.
     
    Last edited: Oct 24, 2010
  16. pranc2

    pranc2 New Member

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  17. patret

    patret New Member

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    [TE=Dillinger;369042]This argument can go 'round and 'round for days, so I will try to take some of the steam out of it with this explanation, not saying I will be successful... LOL

    The Direct Impingement system is the way the platform was designed. It harnesses gas from the round and directly cycles the bolt/action.

    When the M-16 went to Vietnam, there were complaints that it would not work well if dirty/muddy.

    Changes were made, education was initiated and the weapon system moved forward.

    At the same time Good Ol Mikhail over in Mother Russia had developed the AK platform, which was a knock off/copy/ hommage to a German design.
    hs system is a piston, or op rod, type platform. The gas is harnessed near the bore and it drives a piston to cycle the action. As there is less overall travel of gas, the "piston" or "op rod" covers the distance with solid metal and does not allow the same kind of dirt/mud/grime.

    Wars come and go, AK's come to the states, people start getting interested and then we have the AK vs. AR battles/tests/comparisons.

    Someone got the idea of why not combining what is great about the AK, the fact that it will run no matter where you are deployed, with the more familiar AR platform.

    There was money to be made - need I say more?

    From a very novice gunsmith wannabe standpoint, you get this:

    The AK is not as accurate as the AR - regardless of who made each model. If you compare skill level of maker to skill level of maker, the AR is more accurate. The piston system of the AK causes flex in the barrel with each follow up shot, so accuracy is compromised past shot one.

    Adding a "piston" to an AR does the same thing. It is "more reliable" but you are losing accuracy because of the way the cycling of the action must work, you have harmonics along the barrel.

    At street to street, house to house type of fights will this affect the "average" shooter?

    NO! Absolutely not. Out to 50 yards, Minute of Bad Guy is going to be Minute of Bad Guy unless you are trying for a head shot.

    At 200 or 300 yards?

    Yes! A hit with a DI AR might not be a hit with a piston AR. Not that you can't get man sized hits, you can, but the DI is going to be more accurate.

    So, you want to build one. The Piston versions are more expensive currently so if cost is a factor, and I guage that it is by your post, it is going to be cheaper to build a DI edition.

    Personally??

    I live in the Pacific Northwest. We get rain, wind and usually blowing pine needles and "junk" about 8 months out of the year. Now, I have never gone on a three day creep with my AR, or put a lanyard on it and pulled it through a swamp, followed by a sandbox, followed by a wet concrete pour, but I have never had weather conditions cause my weapon to stop working. :rolleyes:

    Could it happen? Yes. If you do not take care of your equipment, any piece of equipment can fail, for the most part.

    For most folks, the benefit of the AK has always been it will run dirty, cold, wet anywhere on the planet and keep heads down with that distinctive chatter.

    In my mind the benefit of the AK has always been the heavier round. Why take the negative, the piston/op rod, and keep the smaller, less powerful AR cartridge?

    I feel the Piston AR's are a solution where the problem was created by people Rube Goldberging something to death. :rolleyes:

    Good luck and feel free to PM if you have further questions on a build.

    JD[/QUOTE]

    Mr Dillinger,

    The reason these post keep going "RE: the m16" is because the Direct Imprigement is a horrible design. A lot of the members know this. There will always be a problem with this operating system. How many Solders and Marines have died because of the M16? You tell me but there is more than one. If you were the one, would you be defending the M16? I hope this post helps some of you and good luck to the rest of you.

    Patret
     
  18. KartoffelSalat

    KartoffelSalat New Member

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    i honestly prefer loss of life to loss of libo.....at least loss of life because of the rifle is my fault....but libo can never be reclaimed, nor is is my fault for not maintaining the rifle.
     
  19. Sniper03

    Sniper03 Supporting Member Supporter

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    urban,

    you may want to be aware that Bushmaster has just sent out a notice this month for owners of the ACR to discontinue use immediately until they are contacted.
    As far as the gas piston system it is a personal preference issue. I am an avid FN and M1-A fan and the gas piston system. However at this time with the ARs being modified to adapt there have been some issues with some. I guess looking at the situation having shot several of them for the money I would stay with the Gas Impingement (DI) as long as you buy a top quality rifle. I have many ARs made by several manufacturers and I will tell you I have a Rock River Elite CAR A-4 that has somewhere in the neighborhood of 30,ooo rounds through her. She is in the 5,000 serial number range to show how old she is I think I purchased her in 2001. I have re-barreled her about two years ago due to throat erosion. But to my knowledge she has had only three or four malfunctions probably caused by ammunition or magazine. I do clean her after every outing whether training, just shooting or hunting. So all systems have their quirks it is as the guys stated personal preference and a funding issue for you. Good Luck and there are some good weapons being made in each format.
     
  20. Dillinger

    Dillinger New Member

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    Mr. Patret - Your position that the M16 is the reason for loss of life holds absolutely no water with me or anyone else that has studied modern warfare. You could have equipped each single soldier with a phase plasma rifle in 40 watt range and people would still have been killed do to the tactics of the other side. :rolleyes:

    The Direct Impingement system is perfectly well designed for the application needed. If you try to pigeon hole it and make it something it is not, then you will find it doesn't fit. Much like trying to take an AK or SKS and make a 1,000 yard sniper rifle out of it. :rolleyes:

    If you read the entire post, you will see there was information on both sides of the issue, but the question was still should an Op-Rod AR platform be a good purchase. As can be seen in several examples the answer is still a very resounding NO.

    Bringing up the state of what happened in the life of any weapon design has little to do with this thread, or any thread that does not specifically ask "what weapon has resulted in the most loss of user life".

    JD