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New DI design I have been thinking about

Discussion in 'General Gun Discussions' started by Dreamcast270mhz, May 28, 2011.

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  1. Dreamcast270mhz

    Dreamcast270mhz Member

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    I have been thinking about a revision to the Stoner Gas system, mainly to help with increased heat associated with the M16 and M4, as well as reducing fouling in the breech/action area.

    The basic revisions I have thought about are: The gas is bled off before entering the breech, in other words as soon as the gas key opens into the action, a set of vertical vents direct the gases upward and away from the internal moving parts. The gas key shape would also change, it would protrude a bit more into the gas tube, and ideally most of the gas would be bled already, and momentum would carry the cycle.
    Don't think of this in your typical AR body, the upper would have a gas deflector, to direct it towards the right, away from any optics mounted.

    Once I draw a diagram detailing the modified parts, it may make a bit more sense.
     
  2. Zak Smith

    Zak Smith Moderator Emeritus

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    Gas pushing on the gas key is not what unlocks and primarily moves the bolt carrier group. It's gas that enters the piston comprised by the bolt and bolt carrier group. The extra gas vents out the RHS of the bolt carrier.
     
  3. Dreamcast270mhz

    Dreamcast270mhz Member

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    Hmm. A few web articles need to be fixed then. What I'm thinking about is isolating the gas from the main moving parts and therefore reduce overall heat build up and make it a bit cleaner. I'm taking a lot of ideas of the ljungman system, although the biggest issue is that design is a tilting bolt. RHS i assume is right hand side, which means the gas exits through the breech.

    What part in the Stoner system actually does the unlocking of the bolt, then?
     
  4. Zak Smith

    Zak Smith Moderator Emeritus

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    What you're describing is basically what all the piston systems do.

    It does not protrude into the gas tube now.
     
  5. Dreamcast270mhz

    Dreamcast270mhz Member

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    The basic disadvantage of the Stoner system is that the spent gas heats the parts up and is why a short stroke piston is used in almost every other NATO nation, because of inherent design flaws.

    The Ljungman system uses a small piece that protrudes into the gas tube, the high pressure pushes the bolt out of the tilt and backwards, and the extra gas is bled up and out, not needing to pass through the moving parts. If you were to combine some of these advantages with the stoner system I see many of the faults in the design corrected.
     
  6. Heretic

    Heretic Member

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    Drop the dust cover and you will see two little holes in the carrier. This is where the gas vents. Pressure behind the rings tries to push the bolt foreward, the cam pin follows it's slot to turn the bolt, unlocking it.
     
  7. tyeo098

    tyeo098 Member

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    this is why my ar-15 bcg is always so dirty
     
  8. Sam Cade

    Sam Cade Member

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    FAMAS: Lever Delayed blowback.
    AKs (former Warsaw nations):Long Stroke
    AK5/FNC : Long Stroke
    G3 type weapons are roller delayed
    L-85: Short stroke (hardly a ringing endorsement)
    FAL: Short stroke but wacky.
    AUG: Short stroke
    G36: Short Stroke
    Vz-58 is short stroke
    MAG/M240 : Long Stroke
    M249/Minimi: Long Stroke
    MG-3 functions on zero point energy or something



    ..and Non-Nato:

    TAVOR is Long Stroke
    Chinese T91 is Short Stroke, as is the semi-mythical QBZ.
    Korean K2 is Long Stroke, the K1 is DI.



    ....and the Swiss use a long stroke (SIG 5xx), because they are Swiss.:D
     
  9. Dreamcast270mhz

    Dreamcast270mhz Member

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    ^ I stand corrected. But still over half are short stroke.

    MG3: Roller Locked short recoil, same as Mg42
     
  10. Apocalypse-Now

    Apocalypse-Now Member

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    what's the difference between the short and long stroke piston designs?
     
  11. WaltonS

    WaltonS Member

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    Short explanation: In short-stroke or short-action, slide or bolt does all the moving, including compression of the recoil/return spring...
    Long-action means that the bolt/slide and barrel compress the spring while together and it decompresses during cycling.

    Someone feel free to correct me if I misunderstood.
     
  12. kozak6

    kozak6 Member

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  13. Apocalypse-Now

    Apocalypse-Now Member

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    ok! i just did some googling, and here's what i came up with on long stroke vs. short stroke:

    the short stroke AR and an independent piston that pushes back on the bolt carrier, and then is arrested, at which point it's driven back forward by a spring.

    this system has the advantage of spreading the recoil forces both forward and backwards, making the gun more controllable under rapid fire. however, the piston spring can wear out quickly, and there isn't as much mass driving the next round forward into the chamber.


    the long stroke has a long piston rod that is attached to the bolt group and is driven all the way back with it, as in the m1 garand. less controllable during rapid fire, less parts, and inherently more reliable, as with the AK47.


    am i right? (i majored in design, it didn't take me long to understand lol)
     
  14. Dreamcast270mhz

    Dreamcast270mhz Member

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    Yeah that about right.

    And the Differences between the Stoner and Ljungman systems-

    Ljungman- Tilting bolt, gas pushes directly on bolt carrier which unlocks and travels back, excess gas vents out top

    Stoner- Rotating bolt, gas pushes on gas key, which allows it to travel into the bolt, unlock bolt and then exit out ejection port.

    The Stoner design has several inherent faults, such as: Heat buildup alters temper of metals, burns off lubricants and warps parts. Tight clearances make dirt, sand, mud more of an issue. Lack of adjustable gas system makes it difficult to cycle under heaviest conditions.

    What I propose to reduce the issues:

    Change the way the bolt unlocks to allow for the following

    Isolate the hot gas from the inner working parts of the system, by directing it up and away from the system before it can enter the breech.


    The way the bolt locks change i propose is simple: Make it so the carrier moving unlocks the bolt, but if the carrier cant move, like during firing, the bolt stays shut.

    With this, it is possible to make the gas key more like the Ljungman system, where it terminates the gas tube and is acted on by the gas moving rearwards, but is directed out and up through the above system in my older posts before it can reach the moving parts.
     
  15. Heretic

    Heretic Member

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    The carrier moving to the rear does unlock the bolt(via the cam pin). If you re-direct the gas, there won't be anything to move the carrier to the rear.I guess I don't understand what you're getting at.
     
  16. JustinJ

    JustinJ Member

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    "this system has the advantage of spreading the recoil forces both forward and backwards"

    Huh? How is that accomplished in a way that long stroke isnt?
     
  17. Bartholomew Roberts

    Bartholomew Roberts Moderator Emeritus

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    Why do you believe that the Stoner design gets hot enough to alter the temper of metals and warp parts?
     
  18. Dreamcast270mhz

    Dreamcast270mhz Member

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    Heretic,

    The point is for the gas to impact the carrier via a cylinder recess inside the end of the gas tube, then at the termination of the gas tube for the gas to be dispersed out a top vent. This is the same way the Ljungman design works and at this point the gas has imparted sufficient momentum for the bolt to fully cycle.

    Bart

    The hot gases progressively heat up the rifle, and aluminum warps a whole lat easier than steel does. The hot gases also have the potential for lubricants to burn off, complicating the issue. Why is it the Swedish had such few problems with the AG42 and we have so many more reports of issues with the M16? Eugene later developed the AR-16 and 18, both with a short stroke piston, and no other NATO service rifle today uses the system, so the other nations must have obviously been concerned with one or more of the faults that are inherent to the design, lending to its mediocre performance against say the G36, or the FAMAS.
     
  19. alemonkey

    alemonkey Member

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    None of the parts that get excessively hot due to the DI system are made of aluminum. If DI caused metal to lose its temper we would be seeing an awful lot of kabooms. The only warping I've ever heard of is if someone runs the gun full auto for an extended period of time and warps the stainless steel gas tube.
     
  20. rbernie
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    rbernie Member

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    It's been pretty well proven (by testing to destruction, with the tests videotaped for all to see) that the barrel of an AR pattern rifle will heat up and warp to uselessness before any other part of the rifle gets hot enough to deform or otherwise malfunction.
     
  21. Zak Smith

    Zak Smith Moderator Emeritus

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    All this talk about critical faults of the AR-15/M16 gas system is somewhat ridiculous considering the M16 has been in service for almost 50 years, and there are rifles such as "Filthy 14" that have gone tens of thousands of rounds without substantial cleaning.
     
  22. Sam Cade

    Sam Cade Member

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    The ljungman system handily avoids the issue of hot gas inside the reciever by venting it directly into the shooters face.




    How hot do you think an AR receiver gets in normal operation?


    Because they are sweden and the rifles were mostly used for parades and such post war. :D
    Both the Swedes and the Egyptians ditched their Ljungman pedigreed rifles the very moment something better showed up.


    M16/M4/C7/C8 rifles are in service in various capacities with most NATO nations.

    Danes in Afghanistan
    http://kaalhauge.weblogs.asb.dk/files/2008/06/livgarden-i-afghanistan.jpg

    SAS in Afghanistan
    http://www.milsim.se/wp-content/uploads//2009/06/sas-group.jpg


    Got cites? Preferably French or German sources.
     

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  23. Bartholomew Roberts

    Bartholomew Roberts Moderator Emeritus

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    You know, I've seen IR videos of M4s doing multiple magazine dumps - 300 rounds and more on full auto and based on the temperature scale, the bolt carrier and bolt never exceed 250F (and that's being generous). So it seems to me that the "hot gases" argument as to internal parts is nonsense since none of those parts are going lose temper at those temperatures.

    What actual evidence do you have that any of things you state are happening (parts losing temper, aluminium warping, etc.) are actually happening? I've read the PDFs of NSWC Crane regarding tests to destruction and watched the videos of several tests to destruction and the only thing I've ever seen warp on an AR15 pattern rifle are the gas tube and the barrel - both of which are made of steel and will last long past the design parameters of the AR15 or any modern infantry rifle.

    I'd guess we have more reports of problems with the M16 because it has been more thoroughly tested/used in actual combat over the past 50+ years than the AG42 ever did in its 20 years as the service rifle of Sweden. Much like the safe queen that sees 250 rounds a year will be "flawless" while the exact same rifle being shot 3,000 rounds in a weekend might not run so smoothly.

    In any case, I'm curious if these assumptions you are making are valid; because I consider myself fairly well-read on the topic and they seem like nonsense to me. So if you have some data that supports what you are saying here, I'd love to see it.

    Yes, because having sold the rights to the AR-15 to Colt, Eugene was going to have a difficult time with patent lawyers trying to build a DI AR-18.

    15 NATO nations and 65 other nations use the M16. As it turns out, the M16 is a fairly successful system - so successful that even many short-stroke piston variants copy it in terms of ergonomics, barrel extension, bolt design, etc. So it shouldn't be a big shock that nations that want a DI military rifle buy an M16 instead of trying to develop their own from scratch.

    And just to nitpick, the new British L129A1 SDM is a NATO service rifle and it uses the exact same Stoner system.
     
    Last edited: Jun 1, 2011
  24. Dreamcast270mhz

    Dreamcast270mhz Member

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    When I say NATO service rifle I mean the standard rifle, as in the most common and numerous rifle fielded by x nation's particular Army. If you break it down for Europe, the countries I remember off the top of my head:

    UK- L85A1
    France- FAMAS
    Germany-G36
    Belguim- F2000
    Czech R- VZ58
    Slovakia- VZ58
    Poland- AK
    Romania- AK
    Austria- AUG

    Now I did look up and indeed there are some militaries that use the C series of M16 derived weaponry. I stand corrected

    What I know regarding France and Germanys current weapon adoption was that the Ar platform had at least one entry, but it was beat out by domestic competitors.

    I have no doubt that the AR is a successful weapon, but the following excerpt from the defense industry daily article says it all:

    I'm not trying to derail my own thread by any means but the fact of the matter is, the AR series doesn't exactly have a stellar track record, from the same article:
    And this isn't 10 years ago, this is much more recent and with this basis I think I'm entitled to make improvements to the design.

    Even if it is not affected nearly as much as believed by hot gases from the tube, using ideas from the ljungman have some clear advantages:

    Reduction in fouling in breech and chamber, reducing need to clean the rifle

    Lowered heating, as a rifle as a general rule operates better at cooler temperatures.


    Now onto the one comment that is puzzling:

    Amusing, but unless your face is directly over the bolt carrier I can't see this happening, since the bolt carrier is a little distant from the comb of the stock, where your cheek lays. Even so, have you actually handled an AG42?

    I have, and while sort of awkward my face was not anywhere near where the breech opens during firing.

    I never made any claims regarding the ergonomics of an AR, they are great and I love my friend's AR, a gas piston variant in .308. I wouldn't, however be able to justify the $1300
    he shelled out for it in my budget.
     
    Last edited: Jun 1, 2011
  25. Owen

    Owen Moderator Emeritus

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    So the action being filled with sand is somehow the fault of DI?
     
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