The ESSENTIAL Guide to Gasses for Gas Guns

Discussion in 'Gas Powered Guns' started by Remoon101, Aug 31, 2011.

  1. Remoon101

    Remoon101 Active Member

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    DISCLAIMER: I DID NOT WRITE THE ORIGINAL COMPARISON. IT WAS TAKEN FROM FROM AAPS-FEDERATION.ORG AND WRITTEN BY Chris Cord, on Airsoft Forum. ALL CREDIT GOES TO THIS INDIVIDUAL.
    OP: http://www.airsoftforum.com/board/Gases-Airsoft-GBB-s-t177920.html

    ---


    This Guide takes an introspective and scientific look into the various gasses used by Airsoft gas guns. While my other guide briefly ran over the basics, this provides more solid information on the gasses themselves. If you notice a discrepancy between the two guides, this one takes precedence.
    I myself included another gas type that is also commonly used but not mentioned in the original guide, Propylene, though I could not find any data to include I believe that it was a necessary addition.
    -Remoon101


    "I've had lots of questions from people regarding gases to use in their airsoft GBB guns. There is a lot of misinformation on the Web related to this issue, so I thought it was time to present some hard science facts about airsoft gases.

    The four gases most used for airsoft GBB guns are Green Gas, HFC-134a, Red Gas, and CO2. Green Gas is also known as Top Gas and is, in reality, nothing more than propane (with some perfume and silicone oil added). The main use for HFC-134a and Red Gas is in the refrigeration industry. Propane is also used as a refrigerant, but is primarily used as a fuel. In the refrigeration industry, propane is known as R-290 and Red Gas is known as HCFC-22.

    [​IMG]

    The properties that make these gases good refrigerants is also what makes them good propellants for airsoft guns. At room temperature and atmospheric pressure they are all gases, but they can be liquified by putting them under pressure. When a gun's magazine is filled with one of these gases, what actually enters the magazine is a combination of liquid and gas (that's why you invert the can to fill the magazine). As long as there is still some liquid in the magazine, the pressure of gas above the liquid remains constant for a given temperature (this is called vapor pressure). As long as the temperature doesn't change and as long as there is some liquid in the magazine, the pressure of the gas propelling your BBs remains constant. Here are the vapor pressure vs. temperature data for all four gases.
    [​IMG]

    It is easy to see from the data why guns with plastic slides need to use HFC-134a (stock TM Hi-Capa 5.1, Western Arms, etc.). The pressure of propane (Green or Top Gas) or Red Gas is simply too high for them to handle unless the magazine valve has been modified to limit the flow of gas. It's also easy to see why CO2 requires a special magazine and valve system. It's vapor pressure at room temperature is more than seven times larger than propane. Using CO2 in a magazine designed for Green Gas (propane) would blow the gun apart when it was fired.

    If you are using an unmodified GBB pistol with a plastic slide, you should stick to using only HFC-134a. If you have a modified gun that includes a metal slide, enhanced recoil spring, and metal guide, then you can use Green Gas.

    Remoon101: FOR DETAILS ON WHICH GASSES SHOULD BE USED FOR WHICH STOCK GAS GUNS, REFER TO MY BASIC GUIDE TO AIRSOFT GAS GUNS

    From here on, we will stop using the term Green Gas and simply say propane. The long-term advantage of being able to use propane is cost. Propane is available through most discount stores and sporting goods stores for less that $3.00 for a 16 ounce can when sold as fuel for camp stoves (Coleman, Bernzomatic, etc.). Compare that to $15 for an 8 ounce can of Green Gas. Of course, you'll need an adapter to fill your magazines. The adapter can be purchased from Airsoft Innovations (Airsoft Innovations) for $25 and is shown below.

    [​IMG]

    If you buy an adapter, be sure to buy some light-weight silicone oil (also from Airsoft Innovations). The oil is added to the propane to lubricate your gun and seals and also to reduce the flammability of the propane.

    [​IMG]

    The adapter comes with instructions for adding the oil and filling your magazines. Another advantage to propane over commercial Green Gas is that the steel cylinders that propane fuel comes in are much safer to transport than the thin-walled cylinders that Green Gas is shipped in. The downside to using propane is that it doesn't contain the perfume that is usually added to Green Gas. Instead of smelling like petunias, your shooting area will smell a little like rotten eggs. (If your spouse complains, just remind him/her of the money you are saving using propane!)

    A word about filling your magazines. If you've followed the discussion above, you'll realize that the pressure of gas in your magazine doesn't depend on the length of time you fill the magazine. As long as you get some liquid in the magazine, the pressure of the gas is independent of the amount of liquid present. The colder the magazine is when you fill it, the more liquid you will transfer to the magazine and the more shots you will get. However, if you get too much liquid in the magazine, then some of it will rush out when you fire the first few shots and spray you and your gun with liquid propellant. This wastes propellant and can damage parts of your gun (like the nozzle and piston seal) that weren't built to handle the pressure increase that results when the liquid vaporizes inside them. With a little practice, you'll find the right ""charging time"" for your magazines.

    Admin"

    Remoon101: There is also a fifth gas type that gives you another option in terms of powering your gas guns. It's called Propylene, and it can often be found alongside Propane in many stores.

    More details on Propylene can be found in this thread:http://www.airsoftsociety.com/forums/f8/propylene-question-27658/

    In terms of power, it is more powerful than standard propane and green gas, but is less powerful than red gas (or not) and less than co2
     
    Last edited: Sep 6, 2011
  2. AirsoftDog

    AirsoftDog New Member

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    Hmm, so if liquid propane bursts out in a vapor sense, is that bad?
     

  3. Remoon101

    Remoon101 Active Member

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    Liquid propane is supposed to vaporize into gas in the first place, so no, it's not bad. It just means your gun is working. Unless A LOT of liquid is bursting out, then something is probably wrong with your gun.

    EDIT: I need some feedback on what people think of this guide as well, rate it, hate it, whatever! If you think I left out something important, I'll do my best to incorporate it into my guide
     
  4. AirsoftDog

    AirsoftDog New Member

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    It's really nice, except the pictures should be placed with the text they refer to.
     
  5. Remoon101

    Remoon101 Active Member

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    Already done, thanks for the feedback!
     
  6. AirsoftDog

    AirsoftDog New Member

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  7. tjhimes

    tjhimes New Member

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    This guide is quite comprehensive, thank you sir.
     
  8. AirsoftDog

    AirsoftDog New Member

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    Maybe add a guide on lubing the gun and places to add oil.
     
  9. Remoon101

    Remoon101 Active Member

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    That's basically covered in my other guide, though I will add a more detailed Basic Maintenance guide later on. This guide is focused more on just the one thing
     
  10. Knief

    Knief Moderator Moderator

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    His analysis of pressure and plastic slides is a little erroneous and simplistic.

    Japanese guns (the usualy suspects are TM, WA, KSC, Maruzen, etc), which are the most common guns that come with a plastic slide, are intended to be used with the lower pressure HFC 134a. This is largely due to velocity laws in Japan. Airsoft guns cannot legally shoot over 1 Joule (328 FPS with .20g bbs), so they design their guns to shoot lower than that. For TM's AEGs, that means the inclusion of a weak spring. For gas guns, that means building them be used with 134a rather than green gas. This isn't just a matter of plastic slide vs. metal slide, however. Many Japanese guns are tuned to be "optimized" in terms of gas efficiency when run on 134a. Anybody who had a WA SVI before the SCW system came out knew that. Even the bulky double stack mags often failed to fire all of its bbs before running out of gas when used with Green Gas rather than 134a. For most guns these days, that's not really a concern. The new gas systems are efficient enough that even on propane/Green Gas, we get enough shots per fill not to care, and hop ups are all adjustable so we can fine tune them for the extra punch that the guns aren't supposed to have.

    The slides, however, can still be a bit weak for propane use. In my experience KSCs tend to be the most resilient of the Japanese guns when run on Green Gas, while TMs, WAs, and Maruzens (you rarely see them these days, but still) are more damage prone. That's probably due at least in part to their association with KWA, whose guns are designed to run on Propane exclusively.

    This does not mean, however, that all guns with plastic slides shouldn't be run with Propane (or at least, that you're risking premature damage if you do use it). There are some Taiwanese made guns that have always been designed to run on Green Gas that come with plastic slides stock. KWC is a prime example of this. Though their guns are no longer held in very high esteem, before KSC and TM released their first M9s, KWC's was the industry standard. As was their Desert Eagle even after TM and WA released their first attempts (both were awful, though TM's latest Desert Eagle design pretty much wiped KWC's off the map). KWCs always came stock with a plastic slide, but because they weren't limited by Japanese law, they were also built to use Green Gas. And in fact, many of their guns either wouldn't cycle or would cycle very poorly with HFC 134a. You had to use Green Gas to use them properly.

    The rule of thumb that this article misses is that Japanese guns, by and large, should be run on HFC 134a (again, not all Japanese guns will explode if you use it, and some, like KSC are quite resilient on it), while Taiwanese and Chinese guns are usually designed to work with Green Gas and Propane, or occasionally CO2 if the design permits.
     
    Christopher Merlo likes this.
  11. ARC

    ARC New Member

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    Knief are you saying that it probably isn't wise to use propane in a KSC M9? And should stick to HFC 134a?
     
  12. Knief

    Knief Moderator Moderator

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    I'm saying neither. There is no do or don't when it comes to matching gas pressure to gun type. What you have to understand when you choose your gas is that you're making a trade off one way or another. Running a higher pressure gas is going to give you better performance (those things like gas efficiency aside, because you shouldn't notice an effect with the newer gas system), but at a cost of decreased durability. The opposite is true as well. Running a lower pressure gas will give you better long-term durability, but you won't be getting the best performance you can out of your gun. A gas gun is just like any other mechanical system. As you increase stress (pressure in this case), you increase wear. It's no different from dropping a stiff spring into an AEG or a putting a turbo charger on your car. You get better performance, but you're going to crack your gearbox/strip a gear/blow a head gasket sooner than if you had left your gun or car stock.

    What you have to decide is how much is your gun worth to you, and what kind of replacement parts are available. If you're in a situation where a $150 gun is all you can afford, and you either couldn't pay for replacement parts or a new gun if it breaks, then maybe you should stick to 134a to be on the safe side. Same goes if replacement parts just aren't available (KSC isn't known for its plethora of aftermarket parts, but there should be some). If you know where you can find replacement parts fairly easily and you don't mind having to replace parts every now and again, then by all means run Propane until your heart's content.

    Like I said earlier, in my experience stock KSC guns hold up remarkably well to propane--far better than stock TM and WA guns at least. I've had 4 different KSC guns (all made before the System 7 implementation, mind you), and ran three of them on Green Gas or propane regularly. None had a problem. Currently, I have two KSC M9s (again, the old system, not System 7) and I've been running them on Propane for like, 4 years, and they've been just fine. Your mileage may vary, both because our guns have different gas systems so my experience won't translate directly to your situation, and because even two guns of the same production line are never identical. Minor differences in manufacturing can mean that two guns manufactured right next to each other might have entirely different levels of tolerance to stress. We are just talking about toys, after all.
     
  13. NSWIntelGuy

    NSWIntelGuy Active Member

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    Great thread! You might be an airsoft nerd if you read this all the way through (or, just a nerd in general)
     
  14. ARC

    ARC New Member

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    Good to know Knief. I think I'll stick to propane then. Especially seeing how you have had several KSCs and haven't had a problem and that was before System 7. I know not everyone has the same exact gun, but they all perform similarly, also I have the System 7 in my M9, so I think that should help more with propane. Although I'm new to the gas guns so I'll find out with time. This is my first gas gun so I still have some more to learn about them.
     
    Last edited: Sep 2, 2011
  15. Knief

    Knief Moderator Moderator

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    Maybe. I haven't done a lot of research on System 7 myself because I've been more interested TM's latest offerings over KSCs, so somebody else might know better than me. But if the System 7 directs more power into the slide, you might be looking at more durability problems with higher pressure gasses. Again, I don't know, and maybe KSC has gone ahead and reinforced their M9 slide to take that extra power anyway. It's just a thought. A newer system doesn't necessarily mean a stronger system. They might have made the same sacrifice of durability for better performance, but they had HFC 134a in mind. If you then run Propane, maybe you'll be pushing that limit even further.

    But again, that's just hypothetical. You should probably do some research on your own on a site like Arnie's for a more definitive answer.
     
  16. Remoon101

    Remoon101 Active Member

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    I think essentially System 7 is supposed to be synonymous with the ns2 gas system. Since KSC/KWA are essentially based from the same original company, and both use the same GBB system (but presented to different markets in the world, obviously).
    And I would think in any case that it would make sense for them to have included a reinforced/tougher slide/internals to compensate. Internals would've been reinforced somewhat for the purpose of the new system, externals like slides, I'm not quite sure.
     
  17. Knief

    Knief Moderator Moderator

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    Indeed. The internals are rarely the problem when it comes to higher pressure vs. lower pressure. The question is, has KSC used a stronger slide or not? Part of the issue may lie in the size of the new blow back unit compared to the old. If the System 7 blow back unit is, say, smaller than their older system, then they likely have a more robust slide built around it for the simple reason of filling space. Similarly, if the System 7 blow back unit is larger than their older system, then they might have a weaker slide due to removing more material to fit the unit.

    Largely, M9s (both real and airsoft) tend to have their slide breakage issues between the extractor and the safety, so this would be the point of most concern (1911s tend to blow out the barrel pushing and any material holding them in, by contrast). Coincidentally, this is right where the blow back unit is. Maybe if ARC and I link up at a game, we can compare out M9s and get a better idea of where a problem might crop up.
     
  18. Remoon101

    Remoon101 Active Member

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    It'd certainly be interesting to see what the results are
     
  19. VirtualWaffle

    VirtualWaffle Member

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    I use propylene, and I find it is only a tad stronger than regular propane. Like 10-15 FPS.
     
  20. Remoon101

    Remoon101 Active Member

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    No one I know of has done an actual chrono test with propylene/propane as of yet. But I've had people tell me about the same thing, usually around 10-20 FPS stronger. Still wouldn't suggest using it in warmer climates though