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AK short stroke gas system

Discussion in 'Rifle Country' started by ndh87, Apr 2, 2007.

  1. ndh87

    ndh87 Well-Known Member

    Has anyone ever made a short stroke gas system for the AK? Something similar to an FAL gas system maybe? What if any advantages would a system like that offer over the regular setup?
  2. Omnivore

    Omnivore Well-Known Member

    The only conceivable advantage would be that the receiver could be slightly shorter. Otherwise, there are nothing but disadvantages.
  3. JesseL

    JesseL Well-Known Member

    The AK already uses a short stroke gas system, so I'm not quite sure what you're asking? :confused:
  4. iamkris

    iamkris Well-Known Member

    What he said

  5. Evil Monkey

    Evil Monkey member


    That post defies what I have learned over the years!

    I refuse to believe that junk.:mad: :cuss:

    AK47, SIG550, etc, uses a long stroke, and AR18, FAL, etc, use a short stroke system.
  6. MMcfpd

    MMcfpd Well-Known Member

    Now I'm confused. Kris, where'd your quote come from?
  7. Hoppy590

    Hoppy590 Well-Known Member

    wow. that just rocked my world.

    im awaiting a follow up explination ( hopefully with visual examples)
  8. JesseL

    JesseL Well-Known Member

    Here is a picture of an AK piston in its forward position, and another picture show how far back it travels before the gas is vented. All motion past this point is driven solely by inertia as the gas pressure as been relieved by the vent holes.

    The AK gas-tube really isn't a gas-tube at all. It serves mainly as a guard and guide for the piston.

    Attached Files:

  9. Evil Monkey

    Evil Monkey member


    I thought the gas pushes the piston and bolt carrier all the way. You mean to tell me that the gas only pushes the piston an inch and the entire piston and bolt carrier start flying backwards!?

    If that's the case, then I really underestimated the power of gun powder.:eek:

    So the gas isn't really pushing the piston, rather it's punching the living daylights out of the piston?
  10. Hoppy590

    Hoppy590 Well-Known Member

    i know where the vents are in an AK tube. but i have the feeling the AK would not operate the same with out the tube. i imagine the tube creates that extra PSI to reliably function the AK. the vent is very small for the amount of pressure introduced to the tube. i cant believe it all vents out those little holes and the rest of the tube is useless again. this is all speculation. so some one show me why im wrong

    added: to say the piston is no longer effected by the gas after the valve is open. s like saying the round in no longer effected after it passes the hole for the gas operation. there still is pressure, albeit decreasing pressure, that operates on both the round and the piston
  11. JesseL

    JesseL Well-Known Member

    Other short stroke gas systems work perfectly reliably with only a fraction of an inch of gas propelled motion from their separate, captive pistons. I don't see whats so unbelievable about the AK doing the same.:confused:

    Not only that, have you seen what a loose fit the piston has within the gas tube? If there were any significant pressure acting on the piston by the time it was back in the tube, it would probably blow past the piston and blow the dust cover off.
  12. Hoppy590

    Hoppy590 Well-Known Member

    bear with me, im a paintball kid. grew up playing paintball. LOTS of experience with CO2, HPA and other compressed gasses. along with shop type experiance so i know that even 1 PSI can have effect. so im just posting questions here. im not doubting. i have no right to doubt. i just want to get things clear, know what i mean?
  13. JesseL

    JesseL Well-Known Member

    What you're forgetting (and I neglected to mention) is that by the time the piston has reached the vents the bullet is leaving the barrel, at that point the pressure is very negligible.
  14. heypete

    heypete Well-Known Member


    The SKS does a similar thing, but the stroke of the piston is a bit longer, but not by much.

    Remember, that the gases in the barrel are under tens of thousands of pounds of pressure per square inch, and are able to propel a ~125 grain bullet at thousands of feet per second. That pressure applied to a heavier piston would certainly get it to move quite quickly.

    Gun powder is very energetic indeed.
  15. fvf

    fvf Well-Known Member

    In my Chinese AK, the gas tube has 8 small holes on the gas tube. 2 4-rows on the front part of the gas tube. Yours seems to have 4 holes around where the gas tube is connected.
  16. 50caliber123

    50caliber123 Well-Known Member

    I thought a long stroke piston was a piston attached to the bolt (AK) and a short stroke piston struck a piston extension (SKS).
  17. BigG

    BigG Well-Known Member

    Regardless of what you call it, the difference mainly is the piston is permanently attached to the bolt carrier on the AK, where the so-called short stroke is more akin to the M1 carbine style piston.

    What the guy is asking is "would there be a way to make it work without the extra mass?" The Dragunov uses almost an identical mechanism to the AK except it has a piston that is unattached to the bolt carrier. The light piston hits a tappet rod a smack which drives the bolt carrier back. The upside is less reciprocating mass.
  18. sharkhunter2018

    sharkhunter2018 Well-Known Member

  19. JesseL

    JesseL Well-Known Member

    Popular (very popular it seems) misconception, but no. The difference is in how far the piston travels under pressure. Short dwell time, high pressure actuation vs. long dwell time, lower pressure actuation. Swift kick vs. gentle push.

    Claiming that the difference lies in the attachment of the gas piston is akin to claiming the difference between diesel and gasoline engines is the connecting rods.

    I wanted to add, I just tried my AK without the gas tube and it functioned flawlessly :D . I did have to be careful in how I held it so as not to give myself a blast of gas to the face :eek:

    This confirms that the AK's piston is only propelled by gas for a short distance and the rest of it's travel is pure inertia. The 'gas tube' is in fact just a cover and guide for the piston.
    Last edited: Apr 3, 2007
  20. BigG

    BigG Well-Known Member

    I was born at night, but not last night - ;)

    I'm sorry to be a wet blanket, but whoever wrote the Wikipedia article you quoted referenced an article on internal combustion engines - for I believe a Sunbeam, a certain authority on automotive engines and of course, directly applicable to firearms discussions (insert irony here). Here is the reference they provided for the WIKI quote above :Sunbeam Tiger discussion of bore vs stroke :eek:

    Below, the words that were somehow twisted by the Wikiwriter to pervert the minds of us firearms enthusiasts. :uhoh:

    The correct firearms related reference appears to be this one: Discussion of long stroke vs short stroke as it relates to gas operation which I've helpfully quoted below -

    Last edited: Apr 5, 2007

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