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How long can you leave a CO2 gun charged?

This report covers:

  • The question
  • Bulk-fill
  • CO2 cartridges
  • The deal
  • Not the full answer
  • The Komplete
  • Summary

Today’s report is an answer to a question reader Decksniper asked recently. Let’s read what he said and I will take it from there.

“Do you or any reader who has tested it care to share their opinion on leaving an unspent CO2 cartridge (88 mm) in a Umarex Komplete air rifle?”

“It is well known that this rifle is actually dual purpose in being able to shoot with either nitrogen or CO2. Ham [Hard Air Magazine] review tests prove it and I use both in my Komplete .177 and .22 calibers. Accuracy is equivalent at reasonable ranges but velocity is far greater using nitrogen as expected. But CO2 delivers an incredible number of useful shots before a cylinder is exhausted. This lowers the cost of shooting to being very reasonable.”

“This gets back to my question. It isn’t practical for me, at least, to shoot 120 to 150 shots with any gun in one outing. I have too many airguns demanding their turn too. I’m hoping the greater hammer spring tension designed for nitrogen offsets the need to remove the CO2.”

The question

The question is—How long can you leave a CO2 gun charged? The answer is—it depends. In today’s report we’ll look at what it depends upon.

Bulk-fill

Sometime in the middle 1990s I bought a Crosman 111 CO2 pistol at a flea market. The lady I bought it from didn’t know how long it had been in the family. She said she found it in a drawer and I think she said it belonged to her late father. As far as she knew it hadn’t been touched in at least 20 years. It came to me in the original box and had the manual and the model 197 ten-ounce gas tank.


Crosman’s 111 bulk-fill CO2 pistol held gas for decades!

I took it home and went to my basement range where I immediately dry-fired it to see if there was any gas left. There was so I loaded .177-caliber pellets and shot about 30 shots before the power started dropping off. I refilled the gun from the tank that came with it. In all I fired several thousand shots before needing to get the 10-ounce tank refilled. The pistol got about 70 shots per fill, so it was about half-filled when I got it — after at least 20 years.

CO2 cartridges

Why then do companies warn us to not store our gas guns with CO2 cartridges installed? Let’s fast-forward to the 1960s. Crosman was making lookalike gas guns like the 38C and the 38T revolvers. The way those guns were made they often required a short pipe to conduct the gas from the piercing pin to the firing valve. That pipe had ends that were prone to leak.

Crosman schematic
This schematic of a 38C/T valve shows the pipe mentioned above. It’s part 38-065.

The deal

So, if there is a possibility of leakage when CO2 is stored in a gun it’s recommended to not store it with gas. The other reason is safety, because anything that’s in the barrel can be propelled by the gas. It’s kind of a loaded gun!

The bulk-fill guns have a seal at the gas port inlet and of course the firing valve is entirely sealed. There is really no good way for gas to escape. Of course all seals fail in time, but bulk-fill guns usually hold gas for a very long time, as you read above.

Most CO2 gas guns that use the smaller 12-gram (and 8-gram) cartridges have pipes like you see in the schematic. That’s true for most guns but not for all. You have to check and see if yours does. And they nearly all have face seals that are thin and prone to tear and leak.

But what about the guns that use those 88-gram and larger cartridges? That’s what Decksniper is asking about. Back in 2014 I wrote about a Crosman 1077 that was converted from using 12-gram cartridges to an 88-gram cartridge—the exact thing Decksniper wants to know about!

1077 rifle 88 gram
My 1077 has an adapter for an 88-gram CO2 cartridge that Crosman used to sell. The round knob at the bottom shuts off the gas flow so the cartridge can be removed from the gun with gas still inside the cartridge.

Stock up on Air Gun Ammo

Not the full answer

That conversion is no longer made. So what about 88-gram CO2 cartridge guns today? Can their cartridges be stored with the guns? And even more to the point, what about those Nitrogen cartridges? Is it safe to store the gun with them? Here is what the Umarex Komplete manual says:

If you choose to store your airgun with a nitrogen cartridge in it, always store your airgun in a secure (locked) location away from unauthorized users and separate from ammunition.”

Umarex addressed the specific question and says that it is okay to store the rifle with the gas cartridge installed, as long as all safety precautions are taken.

The Komplete

I have an Umarex Komplete to test for you and if this question had not been addressed I would have tested it. But I would also have told you beforehand that the rifles that use these large cartridges, both CO2 and now Nitrogen, are built more like bulk-fill CO2 guns than like 12-gram cartridges guns. I would have predicted that it was okay to store the rifle with the cartridge.

Summary

I hope you now understand what “it depends” means, as an answer to today’s question. With this knowledge you should be able to figure this out yourself for each new gas gun you encounter.

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 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.

18 thoughts on “How long can you leave a CO2 gun charged?”

  1. My recommendation if you are going to store a CO2 gun with a cartridge in it, make sure you put a few drops of Pellgun Oil on the tip of that particular cartridge. It will keep the seal pliable and stop the cartridge from sticking to the seal. Guess how I know that can happen?

  2. Tom,

    Knowing that the Komplete is capable of using both CO2 and Nitrogen would it be safe to say that only silicon oil should be applied and not Pellgun oil?

    Siraniko

    • Siraniko,

      Nitrogen does not support combustion, but air does and since the Komplete could be converted to accept high pressure air I’m going to say yes.

      BB

  3. Silicone oil is key to all cartridges. Just one or two small drops on the tip.

    After about 5000 shots I had to replace the valve in my Crossman 2240. When the valve doesn’t hold – oil won’t help…

    For me, stopping shooting means removing the rest of the CO2, if it hasn’t been completely used up, to clean the gun and let it “unloaded” for the next shooting session.

    I understand the question about such a large cartridge. There will be no clear answer – you just have to leave it and check the result after some time. If it holds – great! If not – then you will probably do longer shooting sessions after this experiment 🙂

  4. I believe the ability to leave a cylinder in the rifle is for Nitrogen; Umarex doesn’t really promote the use of CO2 in the Komplete. So it’s going to have to be trial and error to find out if CO2 can be stored without leaking.

  5. Having a large amount of gas left after a shooting session is likely one of the reasons for not having one of these around. I can see where the expense of the gas cartridges would also be prohibitive.

    There is/was an aftermarket valve system for these cartridges that allows them to be removed and retain their contents. One would think that Umarex would have such a product, though I can envision someone using such to recharge the cartridge at too great a pressure and creating a bomb instead.

  6. BB

    Thank you for thoroughly explaining your answer. I will continue to use my two Kompletes as dual purpose for either nitrogen or CO2. If I have any problems I will let you know. By the way, the Umarex Komplete is the cat’s meow.

    The cost per shot for me is reasonable especially when it’s CO2 season (usually 8 months a year). One of the blessings of having way too many airguns demanding shooting time is none gets that many shots.

    Deck

      • I would! Last night, I started the process of my annual gun spring cleaning. Starting with a Winchester 416 (Diana 16), then moving on to a couple of Win. 422’s. I also wiped down the Walther Terrus .22 upon which I had installed an old Beeman scope for testing a while back. I paused my cleaning duties to feed it some Benjamin “Bullseyes,” which I had never tried in it before. It turned in a very respectable .21″ (5.334 mm) group at 10 yards. As good as it’s previously favorite pellet, the JSB Straton from the JSB .22 multi-pack. I also tried fiddling with the trigger adjustment screw, but turning it counter-clockwise just extended the second stage travel, so I cranked it back as far as it would go. I didn’t eliminate the second stage travel, but I shortened it to about 1/8″ (3.175 mm). The good thing about the Terrus is that it LIKES the “deer hunter hold” (firmly into the shoulder pocket and left hand gripping the forestock firmly near the stock screws), so it is good off season practice for my deer rifle. Also good was no barrel seasoning needed. All 10 shots went into a pretty, little (and pretty little) cloverleaf group.

        Ah but I digress, I also wiped down a couple of Winchester 425’s (Diana 25), one of which has a peep sight installed. I took the opportunity to adjust that trigger too, using B.B.’s Diana 27 instructions, and improved the release by quite a bit. Out came the Benjamin “Bullseyes” again and although they made a one hole group, that group was about 3/4″ (19mm). This gun is a beauty, though, in that it makes similar groups with a variety of pellets. The best groups came from HN Excite Plinking pellets if you can believe it.

        Many more guns to go….

    • Deck, the Komplete was interesting when it came out, but I did not see it as a replacement for a PCP (like the 3622 or other price point PCPs) over the long haul due to the initial price of the Nitrogen bottles. But since you are clearly a fan, tell us more!
      1) What is your average price per shot with Nitrogen vs. CO²?

      2) Do you use the same pellet with both Nitrogen vs. CO²? How does the gun shoot with each?

      3) Do you use Nitrogen for different purposes than CO²?

    • Decksniper

      There are a couple of Umarex products you might be able to use with your Komplete rifles that would possibly alleviate your CO2 concerns.

      Umarex still has the 2 x 12g CO2 adapters that work in place of the 88 g CO2 cylinders. If you want to use this adapter, you have the option to use it with 2 full 12 g cylinders or 1 full and 1 empty 12 g to control how much CO2 you use in a shooting session.

      https://www.pyramydair.com/product/umarex-12g-co2-adapter-set?a=9620

      Umarex also has its own 88 g CO2 gas saver adapter that screws onto the top of the 88 g CO2 adapter. With the gas saver adapter installed, you can use as much or as little of the 88 g of CO2, and then remove the adapter / cylinder from the rifle. The check valve in the adapter immediately closes to prevent loss of CO2.

      https://www.pyramydair.com/product/umarex-88-gram-co2-saver-adapter-fits-airjavelin-fusion-2?a=9888

      I’ve used both of these on a few of my CO2 powered rifles. They work very well.

  7. CO2 is a strange molecule it is like water that in its liquid state will dissolve most other fluids ie oils. It will also slowly diffuse into any polymer, the o-rings and seals in the system. Then if the system is rapidly depressurized the seal / o-ring can under go an explosive decompression as the CO2 gas inside the seal will rapidly come out and tear the seal apart. Other gases also do this also but not to the extent of CO2, particularly when in the supercritical state, temperature above 88 F. There is also a time component, the longer the time the more CO2 diffuses into the seals. In addition the rate of diffusion is also a function of the polymer of the seal, some materials the CO2 diffuses relatively rapidly and are more prone to explosive decompression.

    Leaving the cartridge in place should not be a problem if the CO2 cartridge is slowly depressurized by shooting versus a half spent cartridge just being spun open and replaced with a fresh cartridge.

    So my best advice is to use the CO2 up before removing the CO2 cartridge, and store the air gun safely if the cartridge is not removed.

    Mike

  8. I leave all of my CO2 guns charged without any problems.Some are face-seal, like my Plinkster, Chaser, Crosman 782, and Webley Mk VI. A couple use a pressurized tube, like my Alfa Proj and Tau 200. One, my Daisy 887 uses a proprietary refillable 2.5 oz gas cylinder. The only CO2 gun I have that does leak down over time is my QB, which I have modified to use the Daisy cylinders or a RAP4 dual-cart cylinder. It has a very slow leak in the gas block, and I’ll rebuild it soon to fix it. All the other guns hold gas for months at a time. I use a single drop of ATF on each cart when I put a new one in.
    The piercing caps on the Tau and Alfa had Buna N o-rings, which would absorb CO2, and would need to rest before recharging. I replaced the o-rings with urethane, and that problem was solved. I was taught that any seal in direct contact with CO2 should be urethane.

  9. Have left partially-charged CO2 cylinders in the Umarex MP40 for months without experiencing any leakages. When installing the cylinders/cartridges made sure to oil the cartridge tips with the red Pellgun oil. The “house” 38T has been another story. Seem to recall when first shooting it in the ’60s-’70s there were no leaks and many times the gun was left with a partially-charged cylinder in the holder. Ironically, neither the cousin who was the original owner nor FM ever thought of oiling the cartridge tips back then.

    After a rebuild about 4-5 years ago, the gun shot fine for a while, no leaks, pretty much sticking to leaving cylinders inside. Then, even before the revolver had been fired over 60-70 times in a year’s time, upon loading a fresh cylinder one fine day, it leaked down completely. This was traced to the ring around the port into which the cylinder neck fits coming loose. FM tightened it as best he could but not sure the leak gremlin has been fully defeated. Gotta get that Round Tooit and test the gun.

    Just wonder if better-quality materials were used, particularly seals, when the gun was assembled at Crosman around 1965. Maybe that explains why this particular 38T went years without leaking though CO2 cartridges were left inside it all the time.

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