GBBR shooting low fps.

Discussion in 'Gun Building, Modifications & Repairs' started by SilentSamuel, Nov 29, 2021.

  1. SilentSamuel

    SilentSamuel New Member

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    Hey! I'm new to the forum so forgive me if I'm making a fool of myself somehow.

    I bought a WE tech SVD, (I belive they call it an "ACE-VD,") and ever since I got it the thing shot about 400 fps at best. I think it advertised shooting at about 500 but I'm trying for 450 to 475. I'm not sure why it's doing this, though. I've tried a few fixes for gas leaks between the mag and the gun, but they did nothing. I'm thinking about trying a stronger propellant like red gas, but I have no idea if that would work. I currently use green gas. It has the option for Co2 but I'd prefure to stick with green gas as I've heard Co2 can ruin seals. Is there anything else I can try?
     
  2. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Gas guns are very complicated creatures. They are not simplistic at all.

    You MUST know this fundamental physics/chemistry equation:

    PV=nRT

    Know this, know your gas property and you will be an expert gas shooter.

    First off...don't run Green Gas any more. It's just polluted propane with siloxanes and other impurities that robs it of gas pressure. Siloxanes is known in Airsoft as Silicone Oil (BTW...silicone does not exist in an oil form...).

    Also...you can't get Red Gas any more. Red Gas was formerly a Hydrocarbon Refrigerant - R12 - AKA FREON. It is no longer sold in the USA. But, it doesn't mean it doesn't exist in a basement somewhere in MN...or you can buy 20lb bottles of the material from HVAC suppliers and use an "adapter" to fill your gas mags with it...

    And being that this is Airsoft where "standards" don't exist, any more. Most (actually all) US distributors lie or are ignorant on the facts of their products.

    Since there are no standards. US-D make up stuff about the variously "colors" of gasses.

    Green, Red, Black, White, Rainbow...all subject to no standards and US-D just makes up what it actually is.

    To get your best performance run Dry Propane or Propene, yes PropEne (aka...methylene, propylene, this is a double bond propane molecule where propane only has single bonds...yes...HS chemistry) for a nice 12% kick in FPS.

    And where can you get these miracle gases at low pricings...why at a hardware store.
    Propane
    [​IMG]
    Propene
    [​IMG]

    Part two is Temperature. If temps are low...so is your pressure, which means your bb fps is low too.

    Back in 2003 at Savage Garden III in the High Desert of Nevada (7200') in 95 degree temps. My WA Speedcomp II shot bbs at 420fps (.23g) with Propane out of a 7" barrel. If I used real GG back then. My pistol wouldn't fire at all. This was due to over pressure in the magazine. Hammer couldn't depress the release valve to let gas out...

    So, the next question is...what temps are you shooting in?
     

  3. SilentSamuel

    SilentSamuel New Member

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    It was in the low sixties. I'm aware that cold reduces the pressure of gas, but enough to bring my fps down by 100?

    And I heard that running dry propane is bad for the gun. Am I mistaken?
     
  4. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

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    Yes...low sixties can take 150 fps off a long barrel gbbr over say if you shot it at high 80's.

    Look at this Chemistry/physics chart on pressure of propane.

    [​IMG]

    At 60 degrees you are at about 92psi

    At ~88 degrees you are at about ~144psi

    That is a 50% increase in pressure. Where do you think your FPS is going to be?

    See how GBBs are not that "simplistic"?

    You are mistaken, in no way does dry propane hurt a properly maintained GBB.

    In fact GG is more detrimental to a GBB because it is absolutely wrong on how it lubricates (poorly) a GBB.

    If there is oil in the gas. It puts oil in places where there shouldn't be oil (can you think of a place where it would be very bad to have oil touching it?) And does not put oil in places that needs it (areas where are metal bits rubbing together, but the gas doesn't flow there). This is how the US/EU Airsoft Industry is doing you no favors by being ignorant of the facts.

    Plus, a thing with WE's. Their seals are a low grade rubber. Siloxanes eats rubber...so...yes, you are damaging your seals and your mag will leak sooner rather than later.
     
    Last edited: Nov 29, 2021
  5. SilentSamuel

    SilentSamuel New Member

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    Lexington
    I see. Thanks for the info. I knew a gas gun would be more complicated, but I figured I could handle it. Guess I figured wrong. I'll try propane and see if that helps any. Do you happen to know where I can find the nozzle for the tank?
     
  6. Guges Mk3

    Guges Mk3 Administrator Staff Member Administrator Supporting Member Lifetime Supporter

    8,759
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    Minneapolis