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Education / Training A funny thing happened… CO2 gun is a dud

A funny thing happened… CO2 gun is a dud

by B.B. Pelletier

Before we start, there are 3 new articles on Pyramyd Air’s website:

  1. A look inside the BB gun powerplant
  2. Can you bend the barrel if you shoot a breakbarrel air rifle with the barrel broken open?
  3. What is a flyer?

So there I was on the set of American Airgunner. We were filming the CO2 episode, and Paul and I were shooting action pistols at tin cans. Paul had a Crosman 357 and I was shooting a tricked-out Beretta PX-4 Storm with all the bells and whistles. In the next take, we’d be shooting the cans with the camera behind us so we could be seen in the picture, along with the cans downrange.

I had just loaded a fresh CO2 cartridge because the last one ran out during the previous take. The camera started rolling, the director called, “Action!” and we started blasting away. I had one powerful shot and the next pellet came out so slow I could see it in flight. It barely made it to the cans 10 yards away. I kept pulling the trigger and the pellets kept dribbling out. What had happened?

Was the CO2 cartridge empty from the factory? Was it, heaven forbid, a leaker? These things flashed through me mind as the camera rolled, because I had just finished writing Fanner 50, and the memory of leaking CO2 cartridges was fresh in my mind, even though I hadn’t seen one in years.

When the shooting was over and the camera stopped rolling, I went to the equipment table, expecting to remove an empty cartridge. Instead, I exhausted an entire full cartridge! What had happened?

It doesn’t happen often, but sometimes the piercing pin pierces the CO2 cartridge only far enough for just the tiniest amount of gas to escape. When that happens, the gas comes out very slowly. If enough time elapses, the firing valve will fill to capacity and the first shot will be powerful, but all succeeding shots taken immediately afterward will be weak. However, if you wait about a minute, you’ll get another powerful shot followed by more weak ones. The CO2 molecule is very large compared to the atoms of the various gasses in air. So, air may flow well through tiny openings, but CO2 will not.

That evening, back in my room, while answering readers’ comments, I came across this one, attached to a report on how to find CO2 leaks:

“I have a Crosman 357 Co2 powered air pistol. I used WD-40 on the end of one air cartridge before knowing what sort of harm it would do to the airgun (that was a stupid idea).

Now the airgun is no longer consistent with each shot I fire. i.e. I fire one shot and its perfectly normal, then I fire another shot and the velocity of the pellet goes down by half etc… But when I wait for about 60 seconds after each shot the velocity of the pellet returns to normal. I don’t hear any leaks and I just got this gun about a month ago…

Would Crosman pellgunoil fix this problem? Or would this problem fix itself over time? What would you recommend?”

Those words brought the problem into sharp focus! Although I hadn’t thought about it much, I now remembered that this sort of thing happens from time to time, even with modern CO2 cartridges that are entirely reliable.

Here’s what I’m saying. The use of WD-40 is not recommended in a CO2 gun, but I’m not saying it had anything to do with your poor gas flow. I think you did what I did, by allowing the piercing pin to not penetrate the CO2 cartridge far enough to allow the gas to flow as it should. It could get out, which is why, after a minute or so, you have a powerful shot. But the next shot will be weak because the gas can’t flow fast enough to build the kind of pressure the gun was designed for.

Your problem with this gun is mechanical, and it may also be procedure-based. It’s mechanical because the pierced hole isn’t as large as it needs to be, and it may be based in a faulty procedure if you are not adjusting the piercing mechanism so that it pierces the cartridge in the way it was designed to.

In the 1960s, there used to be a special instruction in the manuals of some CO2 guns on how to effectively pierce cartridges. You were to screw the piercing cap down until you heard the hiss of escaping gas, then UNSCREW the cap a quarter turn, if you could. If the gas was not escaping fast enough, you would be able to easily unscrew the piercing cap, because the o-ring that sealed the gas in the gun was not under much pressure. Hence, the cap could turn. That was your signal to do something, which meant re-pierce the cartridge. However, if the pressure was high, that o-ring was tight against the side of the reservoir wall, making it impossible to turn the piercing cap by hand. That was the proof that the escape hole was large enough.

Piercing mechanisms have changed since those days, but the object has remained the same. Create a hole large enough for the CO2 gas to flow freely. Remember that each time you install a new cartridge. And oil each new cartridge with Crosman Pellgunoil–ONLY!

author avatar
Tom Gaylord (B.B. Pelletier)
Tom Gaylord, also known as B.B. Pelletier, provides expert insights to airgunners all over the world on behalf of Pyramyd AIR. He has earned the title The Godfather of Airguns™ for his contributions to the industry, spending many years with AirForce Airguns and starting magazines dedicated to the sport such as Airgun Illustrated.

39 thoughts on “A funny thing happened… CO2 gun is a dud”

  1. I have a CO2 question that is related to this topic. I just acquired a 2250 in a trade. The 2250 has been modified with a brass breech, poly tube, and a heavier striker spring. I am pretty sure that there has been some valve work as well. When I install a new CO2 cartridge, I have to use a screw driver to crank the cap down to get the cartridge to pierce. When I start to hear gas flowing, I have to quickly give another quick 1/8 turn or the gas will continue to leak out. I have to install the cartridge with the bolt cocked or the hammer spring would hold the valve open and immediately empty the cartridge. I have asked on other forums and tried all of the suggestions that were provided with the same results. I have tried hand tightening the cap with the bolt open and then dry firing. Nothing seems to work other than cranking the cap down. After I do that, the gun holds gas indefinitely. I went ahead and ordered a new valve and spring from Crosman to return it to a stock configuration, but does anyone have any idea what is happening? This is my first CO2 gun, but I have done a lot of reading and research, so I feel like I have a decent idea how these things work.

  2. UW Hunter,

    I suspect the face seal that the CO2 cartridge bears against. If the person who modified the gun also installed a "better" face seal material that is thicker or harder or even both, that would explain why you have to do what you are doing. Obviously (it seems to me) the piercing needle isn't piercing the tip of the cartridge deeply enough.


  3. UW,

    There's really not that many options for what's going wrong with your gun. My best guess is either the piercing pin is too short or the valve spring is way too long.

    Jump on Crosman's website and download the EVP manual for a Crosman 2240. Take a look at the valve diagram and you'll see what I mean.

    If it was mine, I'd disassemble the valve and remove the valve spring (Crosman part #788-061) then substitute a slightly shorter spring from the hardware store that's similar in all other respects.

    You could cut a coil or 2 off the valve spring, but since you don't know yet if it's bad, you might as well save it.

    If that still doesn't work, then I'd have to assume that the piercing pin (Crosman part # 2250-016) is too short to reliably pierce the cartridge.

    Folks typically modify the valves by opening up the inside of the valve body as well as thinning the pin assembly to gain volume. This get more Co2 into the valve thereby increasing the power (Sometimes. There's other variables at play, too–like barrel length) So, it's possible that the tuner pointed up the tip of the piercing pin and inadvertently shortened it too much.



  4. something is wrong with the way you are loading the cylinder. You should not here any gas flow until after you take the first shot. Piercing the pin should occur after you have seated the cylinder and made the first shot….it should not be opening when you turn the cap down

  5. Hello B.B.
    excellent topic on the CO2.
    I have a question regarding CO2 airguns. I was in Indonesia last month for vacation and my uncle owned a crosman 1077. Pellgun oil is not available in Indonesia – at least I wasn't able to find any, so would motor oil for cars or motorcycles be a good substitute to use on the tip of the CO2 cartridges?
    Another question comes to mind. Does crosman sell repair kits for the seals of the crosman 1077? We left a CO2 cartridge in the rifle for more than a week, and the next time we filled it, the CO2 leaks and we can't shoot the rifle anymore. We found out that the white teflon seal is cracked/broken inside. We talked to some shop owners there in Indonesia, and they say the seals break when CO2 cartridge is left in there for more than a week.

    Here in the U.S. I own a crosman 357 and leave it charged for more than a year (with a drop of pellgun oil in the cartridge like you always say) and I haven't had any leaking problems.


  6. I was becoming suspicious of Crosman cartridges, and this is tending make me believe those feelings.
    I've been happily shooting Walther CO2 cartridges in my two pistols (a PPK/S and a CP99) for about a year. Probably gone through 50 cartriges.
    A couple of months ago a friend picked up Gamo V23 and a pack of Crosman cartridges and came by to sight it in.
    Out of a pack of 12, 5 cartridges were faulty…just as you describe in your post. A couple low power shots then nada.
    We sent the pistol back as it was obviously faulty and under warranty…but it was sent back with the note "could find nothing wrong…worked flawlessly when tested".
    Well lo and behold my dealer ran out of Walther product last week and I bought a pack of Crosman CO2.
    This past weekend loaded up the PPK/S and….one so-so shot and the rest dribbled out of the barrel. Tried another cartridge and it worked fine.
    Loaded up the CP99 and it worked great…until the 3rd cartridge.
    Same thing.
    Me thinks Crosman had a production foul up recently.
    CowBoyStar Dad

  7. I had something similiar happen on my 1077. I always use a drop of pellgun oil on the tip of the CO2 cartridges. Also, I only screw the CO2 cap on a little at a time until I hear a hiss or until I pull the trigger (unloaded and pointed at the ground) and hear a good solid pop. Once I had to turn the CO2 cap a little bit more because it took so long to rejuvinate between shots. The reason I pull the trigger ocassionally when installing a new CO2 cartridge, is because I tighten up a CO2 cartridge too tight one time and had a hard time removing it. If you miss the hiss your screwed.

  8. CowBoyStar Dad,

    You are correct! I've got a box of them that arn't piercing properly also. Yes, it's a new box of the cartridges. They are doing exactly the same thing yours and B.B.'s were doing.

    Mr B.

  9. Derick38, I have ordered the stock parts from Crosman which should fix the problem. I want to take the thing apart to try to diagnose the issue, but the stupid little allen screw in the breech is stripped, so I ordered a couple of those too. I don't want to take anything apart until I have replacements.

    I don't know what I could possibly do wrong when loading the cylinders. I have tried to finger tighten the cap and then dry fire the gun to pierce the cylinder. I keep tightening the cap and dry firing with no success. Eventually I have to use a screw driver to continue to tighten the cap and finally it will pierce the cylinder and I can hear gas escaping immediately.

    When I get my replacement parts, I can return the gun to a stock configuration and look at this valve to see what's going on. I really want a lower powered, efficient gun, not a gun that is modified to be as powerful as possible. I have a Disco for my hunting gun.

  10. Derrick38,

    I wouldn't think the piercing pin is too short on UW Hunter's gun. I just measured my 2250 type factory valve, and the end of the pin sticks out past the powerlet seal's seat 0.0315" (about 1/32", no seal in the valve). So to pierce the cartridge by just cranking the tube cap down would flatten the powerlet seal to less than 1/32" (with the standard puncture pin) and probably damage it.

    UW Hunter,

    I'm guessing that seal needs to be replaced and it will work fine. As Anonymous said about the 22xx powerlet loading procedure, tightening the tube cap is not supposed to puncture the powerlet. It is the first shot. On the first shot, the striker hits the valve stem to open the valve. The puncture pin is connected to the opposite of the valve stem so it pushes into the powerlet thereby puncturing it at that point.

    A.R. Tinkerer

  11. That last sentence was supposed to say,

    "The puncture pin is connected to the opposite end of the valve stem so it pushes into the powerlet thereby puncturing it at that point."


  12. AR,

    Yeah, I wouldn't think the pin is too short either except it's not piercing…so it's at least in the realm of possibility.

    I was thinking a too long valve spring had been installed by a previous modder and it was coil bound–thereby not allowing the pin to come forward enough to puncture the cartridge.

    BB's idea that the valve end seal is too thick is also good. It's just not nearly as common for valve modifyers to make a new end seal, so I left that out.

    Anyway, all this is definitely on the right track and UW should get it sorted out soon.

    Keep us posted UW, this kind of thing is bound to happen again to one of us.

  13. A.R. Tinkerer

    I have tried to allow the first shot to puncture the cartridge, but it will not do it. I cannot get gas to flow at all unless I crank it down. I looked down the tube and I can't see anything that would puncture the cartridge with the bold open or closed or while dry firing. This is my first CO2 gun, so I don't have anything to compare to. I have studied the parts diagram and I understand how it is supposed to work, but it does not work as it was designed to. It is frustrating getting a gun that someone else has modified. I don't know who did what to it, but that's also part of the fun I guess. Will the new valve assembly come with a new seal? I hope so. I asked the person that I got the gun from about this problem and I didn't get a response. I can't imagine that I will still have the problem after I replace the valve and spring, right?

  14. Hi B.B.
    Going a bit off-topic here, is there any durable springer in the RWS 34 Panther price ranger that compares in quality?
    I need to be really careful in my decision on which air gun to buy since I am in Brazil and getting a permit to import one is a pain.

  15. Hi, I'm looking for some advice on how to lubricate my Daisy 15XT co2 airpistol.. The seal that the top of the co2 cartridge connects to leaks a bit. Would it be ok to use silicone lube designed for airsoft guns on the seal, as i don't have any crosman pellgunoil on-hand.


  16. UW Hunter,

    Wow, if it doesn't puncture at all on the first shot, that helps narrow it down (I didn't understand that). That points to the puncture pin, valve spring or seal problems that Derrick38 and BB mentioned.

    Yes, I believe the valve assembly will come with a seal. If not, it is Crosman part# G397-012.

    It doesn't seem like you should have a problem after replacing the valve and spring. The only places it can leak, other than the valve, are the transfer port and bolt.

    Sorry your first CO2 airgun has given problems!


  17. For those buying a new co2 gun always check the piercing pin for damage. I bought a crosman c11 with what seemed to be a piercing needle that was machined wierd. (looked liked a normal pin that has been machined in half) it leaked and I ended up destroying it in anger.

  18. BB,
    I liked the article on the BB gun powerplant.

    My sole CO2 "sidearm" is an old Daisy Powerline 1200, which in perfect weather shoots about as accurately as a shotgun. I can't stand having the point of aim change with temperature, either.

  19. Hi,Way off topic this but does anyone know how to up the power on a Brockock air cartridge also known as TACS (tandem air cartridge system)they were used in the Saxby&Palmer range of rifles/pistols as well.
    Many thanks,

  20. Anonymous looking for advice on how to lubricate his Daisy 15XT C02 pistol,

    Please don't use silicone lube. Here's a quote from B.B., "If not Pellgunoil, then 20-weight non-detergent motor oil. Nothing else! Read this to see where and how the oil: /blog/2008/09/what-to-oil-part-1-a-guide-to-sealing-pneumatics-and-co2-guns/ …"


  21. Nicholas,

    You won't find a better value for a new, powerful, beakbarrel than the RWS 34.

    Have you used the search box on the right to find the articles and comments that B.B. has made on the RWS 34? Have you had a chance to read all the reviews on the rifle from people who have purchased this gun on the Pyramyd AIR site? Lot of good information that should confirm your research and instinct that this is a good one.


  22. Question for any and all.

    Started the Daisy 953 mods yesterday and already made my first mistake.

    What lube should I use on my Daisy 953 hammer? It was factory lubed with a clear light weight greese. Unfortunately I let it get a bit of dirt on it and had to wipe it out. So I need to put in new greese.

  23. kevin,

    Thanks for the confirmation, I really just want to make sure that I have looked at every possibility before purchasing. In a few weeks I'll probably another happy 34 owner.

  24. Bassman,
    Please accept my apology for my comment yesterday. Would have extended my hand sooner… but I only get to read this late at night.

    But… the comment really was not all that brazen… it was intended as advice. Proper targets are really very low cost. It adds only a penny or so per shot.

    I myself have been guilty of attempting to find a printer paper that punches clean. Tried card stock and such. But nothing works like real proper targets.

    I’m glade other offered you advice you found more useful.


  25. BB,
    I just came back from yellowstone (nothing special by the way except for gysers and wildlife) so I'm catching up. I read your post about the things to look for in the future, just my 2cents.

    I would try and harness that energy used to make the air rifle travel faster and chanel it into a semiauto air rifle (FX semiautos in mind)…airguns are powerful enough to to the job as it is. Why not focus on making action pistols and hunting airpistols more powerful?
    Shadow express dude

  26. Nicholas,

    PLEASE don't take my word. I would rather empower you than be responsible for a decision you alone should make. Here's a link, that you will have to copy and paste, that will take you to an article that B.B. wrote awhile back titled, "Pro-Guide spring retainer system for RWS Diana rifles":


    In this 3 part article (click on parts one and two at the top of the article to read them in sequence) you will learn about a "drop in" system that will allow you to home tune your gun. It may increase velocity but it will definately make your gun tamer and more accurate. As important, within this article you will find a paragraph titled, "What's next?".

    In this "What's next?" paragraph you will see links identified by a few words that are underscored. You can click on these underscored words and you will be routed to more information. Within this paragraph if you click on ".177 RWS Diana Panther" it will take you to the gun for sale on the Pyramyd AIR website. Scroll down to the bottom and you will be able to read 38 reviews of the gun by the new owners of RWS 34 Panthers. If you click on the words, "I tested for you" it will take you to the wonderful 4 part series of articles that B.B. wrote on the RWS Diana 34. If you plan on putting a scope on your new 34 click on "Leapers Scope Base" and you can read about the Leapers Scope Base that B.B. (and Mac) helped design specifically for the RWS Diana guns. You need this scope base if you are going to put a scope on your 34.

    Good luck in your research.


  27. B.B.

    I just saw your comment on me sending you my info on the coconut oil testing I've done..
    Your email address was lost in my computer crash.. You still have mine, I think so send me one and I'll send you back the info on coconut oil. I do have a few different guns and pellets tested now.

    Wacky Wayne

  28. Nicholas,

    The "library" of archived airgun information on this site is almost bottomless and you don't need a library card to access the information. B.B. has written over 1,100 articles and there are conservatively 50,000 comments. Every article is a wealth of information and many comments contain good information.

    By typing in the subject you're trying to research in the search box on the right you will automatically search the articles and comments that will more than likely provide you the answers.


  29. DB – probably litium, just use something light and white or spray lube or dry lube and polish it out. Other greases and heavy lubes can slow the hammer and velocity.

  30. Dave,

    The TAC has been engineered to not go above 12 foot-pounds because of UK law. One way to get more power would be to create a longer cartridge with a larger air chamber inside.

    The TAC would be very difficult to modify because it has been engineered to a standard power.


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