Why is Co2 not effective for automatic gas blowback?

Discussion in 'Gas Powered Guns' started by Dead_Christmas, Jul 25, 2021.

  1. Dead_Christmas

    Dead_Christmas Active Member

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    I have heard from one user, who's likely to be the first to reply to this thread. That Co2 is inferior to gas like propane, 144a, etc. particularly in combating cooldown in automatic fire. Is this true?

    Thanks
     
  2. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Absolutely inferior, unless you have a large reservoir to mitigate heat bleed off...it's a terrible gas. 12 grams is is not much material...it's less than 1/2 an ounce.

    I know people want it to be a great gas for rapid fire...but physics is not supporting their misconception. If CO2 was good. HPA-Compressed Air would never have supplanted it...it's that simple.
     

  3. Dead_Christmas

    Dead_Christmas Active Member

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    [​IMG]

    So the biggest problem is that it's just not enough? What's that about heat bleed-off?
     
  4. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Hey Erik Estrada!

    Ideal Gas Law Sums it up in practice - PV=nRT

    (Note: I am piecing together data and I "know" I am not exactly applying it right, but I am setting the frame work on why CO2 is inferior to Propane)

    CO2 - Heat Needed to convert it from liquid to gas at equilibrium under pressure

    https://www.engineeringtoolbox.com/...conductivity-temperature-pressure-d_2019.html

    At 8.3 Degrees F it takes 0.09887 BTU's to change it from liquid to gas.

    While propane at about the same temp

    https://www.engineeringtoolbox.com/...-propane-Cp-Cv-isobaric-isochoric-d_2060.html


    At 8.3 Degrees it takes 0.03564BTU's to change it from liquid to gas 1/3 of the "heat" energy.

    Then on top of that the triple point where gas could change to liquid is much lower...unlike CO2.
    CO2
    [​IMG]
    Propane
    [​IMG]

    The inside of a CO2 Jet can rapidly hit that temp under rapid fire.

    CO2 will never be the good gas source for Airsoft.

    There is a statement I use often that if we don't know of our recent history we are doomed to make the mistakes of the past. Paintball went through the whole CO2 issue in the 1980s from 12g to 20oz tanks and then HPA.

    Other supporting info:
    WHY DO CO2 CARTRIDGES GET SO COLD?

    https://www.genuineinnovations.com/blogs/learn-about-our-tech/why-do-co2-cartridges-get-so-cold

    Co2 Paintball Tanks vs Compressed Air (HPA)

    https://www.paintballruinedmylife.com/paintball-help/co2-paintball-tanks-vs-compressed-air-hpa/

    Leave it to the French to totally screw the Airsoft industry over for 2 decades...by being Physics and Chemistry Deniers...
     
    Last edited: Jul 25, 2021
  5. Dead_Christmas

    Dead_Christmas Active Member

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    Holy ****, wasn't expecting *that* good of an answer.

    I thought Co2 didn't liquify at all, though?
     
  6. gunnerk19

    gunnerk19 Active Member

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    CO2 as a liquid exists below the critical temperature of 31C or 87.8F. Siphon tanks were widely used long ago on paintball guns like Tippmanns that ran on liquid CO2.
     
  7. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Liquid also formed under high pressure....as noted on the chart. But, take that to a cold temp and a low molecule count it turns into a solid and you have no pressure.
     
  8. Dead_Christmas

    Dead_Christmas Active Member

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    Thanks guys. Does Co2 have any advantages over 134a, or HPA?
     
  9. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    No.

    HPA replaced CO2 for a reason...and its all cited above.

    134 is like propane. Just at lower pressures.

    CO2 is the wrong gas for Airsoft...
     
  10. Dead_Christmas

    Dead_Christmas Active Member

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    So I assume it's because Co2 was already around for a long time with airguns, and the powers that be decided that it was convenient and simple enough for anybody to use? (Simple enough, maybe not so much).
     
  11. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    It was also an aspect or Big Box Shelf Space. It was easier to hang a product next to High Margin CO2 jets with no large space requirements for cans of gas.

    Plus, they are more foolproof over a gas mag where the temp of the mag must be colder than the fill tank. I get kids now and then on the field complaining about only getting 5 shots from their gbb.

    Then when I fill it I put gas in, vent it and then fill the mag after the vent...they go...umm..why did you vent it...then I give them a physics lesson of PV=nRT.
     
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  12. Dead_Christmas

    Dead_Christmas Active Member

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    Do you have to fill it full before venting? Does that work at all temperatures or only if it's warm out?
     
  13. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    As long as the Fill tank is warmer than the mag. Liquid will always transfer over.

    Mag can be 90 degrees, but if the fill tank is 110, liquid gas will transfer over.

    But, if the tank is 90 degrees, but the fill tank is 80. You are not getting much gas over and you will definitely not be filling it up to vent.
     
  14. Dead_Christmas

    Dead_Christmas Active Member

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    Is there an optimal temperature of each object for this process?
     
  15. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Ideally yeah...in practice with humans doing the transfer...no.

    As long as you have a gradient in a temp variation between the two vessels. It will transfer...
     
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  16. Dead_Christmas

    Dead_Christmas Active Member

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    I mean, is there the possibility of it not being vented completely because the temps aren't optimal? Like, if one were trying to vent a magazine, would they want to fill it with as much liquid gas first, and warm it up so as to make the entire tank full of just gas for a more thorough venting?
     
  17. GrimWolf0770

    GrimWolf0770 Active Member

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    I started venting gas when you said to chill Gas mags,I wondered if anyone did this. Now do you let the gas out slow or one big burst?
     
  18. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    If you have a CO2 paintball background...you would know to do this especially if you filled your own tanks.

    I just let it out in one big burst, there shouldn't be much in there. If there is a lot of gas in there...then you really didn't need to chill it down to fill it.
     
  19. Dead_Christmas

    Dead_Christmas Active Member

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    Is there any way to know if a magazine needs to be purged? I've never had a gas magazine since 2014 that "stopped taking gas", except for a KJW M1911A.
     
  20. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    If the mag is warmer than the fill source, then you can use the gas purge method to cool it down quickly.

    Or like heavy gas gun users do on fields. They bring a cooler full of ice water and baggies. they toss in the warm mags and 3 minutes later cool to fill without purging.

    Thing is...Gas gun usage is not simplistic like say an AEG or a springer and the fundamentals of Gas Law is handy to have when you operate your GBB.