Can a CO2 gun work with air?

by B.B. Pelletier

We got the following question posted to Friday’s blog:

“This question is both for the Chinese Crosman copy [the QB 78] and the Drozd. Is there a way to convert such weapons to use compressed air, such as a fillable tank?

The quick answer is yes, a CO2 gun can be made to run on air. As long as the pressure of the air is not too different than the pressure at which CO2 normally operates (853 psi at 70 degrees F), then the valve will open with the same hammer weight and spring strength. Once open, the thinner air, which is comprised of several elemental gasses, flows through the valve faster than the large CO2 molecule, so the velocity will spike. Because the air flows more freely, more air than CO2 gas will flow. The pressure will drop faster, resulting in fewer shots. Also, the CO2 in a reservoir is a liquid that evaporates into gas, maintaining the pressure of the gas. Pressurized air is just a gas; and when it’s gone, there’s nothing to replace it.

It’s been done many times
I’m sure this has been done by many experimenters, but the first one I’m aware of was one that Dennis Quackenbush did in the mid-1990s. A .22 caliber Quackenbush Excel that got about 650 f.p.s. on CO2 jumped to over 800 f.p.s. on air. An air reservoir of nearly the same size as the CO2 paintball tank got far fewer shots per fill, but enough to make the experiment worthwhile.

Air Arms S200
You may be more familiar with the Air Arms S200 PCP rifle. It started life as a Tau 200 CO2 target rifle that several American field target shooters decided would make a good PCP gun. At the time, the rifle was selling for about $275. Several people began converting Tau 200s into PCP rifles, and they worked well enough that they caught the attention of Air Arms. They contracted with the Czech factory to produce the rifle under their name, and the S200 was born. By passing through another set of hands and with the increase of the euro against the dollar, the price has risen quite a bit.

Steyr CP1/LP1
Several years ago the Steyr company contracted to make their popular 10-meter target pistol, the LP1, into a CO2 gun with Barbara Mandrell’s name on it. Starting in 1999, It was sold through the NRA to raise money for USA Shooting, the American Olympic contingent. Steyr used a CO2 valve and a CO2 tank. Why the gun was requested in CO2 is a mystery, since PCPs had taken over the world stage when the pistol was first offered, but Steyr also offered the parts kit to change the gun to a PCP through Steyr dealer Scott Pilkington. Though 250 were scheduled for production, the actual number produced was probably close to 100, because the price was perhaps too high for non-airgunners.

The Barbara Mandrell Steyr pistol was available in either CO2 or PCP.

Both the QB78 and the Drozd have been converted to air
These days, making such conversions is easier because of the paintball crowd and their constant-air technology. They have regulators to lower air pressure for the firing valves in their markers to 850 psi, which makes a gun run just as efficiently on air as it would CO2. By controlling the volume of the firing chamber, they can also control the potential power of the gun. As long as the valve can pass only a certain volume of air, it cannot exceed a certain power level regardless of the valving it has. It doesn’t become more powerful on air than on CO2.

This paintball technology transfers over to airguns very nicely. It’s been done on the experimental level, and the small production level with the QB78 and the Drozd, but no big company has yet employed it. I think they will, when somebody realizes the potential for greater sales.

23 thoughts on “Can a CO2 gun work with air?

  1. I can tell you first hand that the Drozd works great on High Pressure Air (HPA). There is a drawback though. Be prepared to spend as much money or more on the HPA tank and accessories as you did on the gun itself.


  2. Is there anyone who has done some hop up work to a AR6 rifle? What I’m looking for is some sound moderation for U S application.


  3. Curious,

    Are you aware that someone just got 15 years for selling a silencer with an airgun? The circumstances were against the defendant, but a precedent was set.

    Why not just buy a legal silencer and put it on the AR6? Then you are in compliance with the law, no matter what happens.


  4. BB

    I was banking on the strong possibility that I would be refused the license for silencer.

    I have large rodents and tree hugging neighbors.

    Is the license for silencer unreasonably difficult?


  5. OK,

    So maybe I will look to another way of acheiving my goal…
    Can a Raider venom be modified to perform closer to an AR6 in terms of ft. lbs. and noise? Legally for California of course.

    I’m just asking if the odds against applying for a license and getting one for the silencer are greater than successfuly modifying the rifle to be a quiet performer, legally.

    what think ye?

  6. I’m glad the subject of converting CO2 guns to air has come up. I looked into this and found some of the information was difficult to find. The following were the main difficulties.
    1) Converting the CO2 connection to a paintball ASA connection.
    2) Finding paintball tank regulators that provide more than about 800PSI.
    -Air America Armageddon
    -Air America Raptor
    -Air America Apocalypse
    -Smart Parts Max-Flo (not the micro)
    3) Finding small 3000PSI tanks.
    4) Finding the above tanks at a reasonable price.
    5) Putting together the parts needed to keep things safe (bleed valve, on/off valve, burst disks, etc.)

  7. my pair of crosman ebbs have both broken down (big surprise), and i’m looking into buying a gbb for casual plinking. i’m in canada, so i cannot order from pyramyd (though i would in a heartbeat after all of the praise!). i’m taking a plunge and buying online. the dealer is the airsoft canada armoury, stemming from a few canadian forum moderators. i’ve narrowed it down to the ksc mac11 and the ksc g18. i’d be very happy with both pistols. i pick these two because i’ve heard that the plastic bolt on the ksc will shatter with propane/green gas use. i dont have the cash to shell out for the upper reciever/ bolt upgrade, as i’m buying a computer as well, and i’ve already cut down on the graphics card for these. i know tom gaylord did a review, and i think you wrote one, but i cant seem to find it on the search —two part comment…wow.—

  8. (hey, i’m probably imagining again).
    ah, and i’ve also heard the new version of the ksc mac has the magnesium bolt. i’ve contataed asc to confirm this. is this true? and, what is your opinion of the two? i know the mac is superior in terms of sound and rate of fire, but i only wanted a gbb so it would not break down on me, and a shattered bolt does not sound sppetizing at some $300 canadian (propane adaptor, too). thanks for the blog and your help!


  10. some more digging and i found a review of the mac11….. the owner saying his g18 eventually failed by a cracked slide! does this mean BOTH need to be upgraded to properly function (with propane)? if this is the case, i will probably need to step down yet another notch on my pc and will definetely shell out for the mac.

  11. Totally off topic, but I was wondering what brand of scope would you recommend for my Gamo Shadow Sport i think is the model? I was looking at a Barska, a Tasco, or a Gamo although a buddy of mine is trying to convince me to buy his Crosman scope. Would you recommend some other brand? All those scopes I could find for about 25 bucks at my local academy (the Crosman scope is 15 from my friend).

  12. hello,B.B. Pelletier,
    thank you.

    and my email is
    also was the MSN.

    best wishes!

  13. Raider Venom,

    Can it be adjusted for more power? I don’t think so. But 860 f.p.s. in .22 is very powerful already.

    If you are a California resident you cannot legally own a silencer. California is one of the states that prohibits their ownership.


  14. dm20,

    Your research is way ahead of anything I know about these guns. Here is my suggestion. Buy the gun you like and just use it. If it fails, buy the upgrade to fix it at that time. If it doesn’t fail, you are ahead.


  15. yeibon,

    That’s not how we work. All discussion is here on the blog.

    Before you build a Talon by yourself, you shoud repair some pneumatic guns first, to learn how they work. Same for pumps. There is very little literature to help, but the book I recommended a few days ago is a good place to begin.


  16. Thank you for covering this subject in brief B.B.!

    I spent quite a bit of time researching information about this subject before converting my RWS 850 to air. Even at that I just used a 3000PSI paintball tank, the regulator that came with it and a braided stainless steel hose remote setup. Most of the relevant information is on paintball web sites. Safety is an important concern!

    I found that to go much further would require learning about machining, metal properties, adhesives (loctite), seals, lubricants and even physics and math. Someone who wants to learn more should pick up a book like “QB78 Family Workshop Manual”. I probably will!

    .22 multi-shot

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