by Tom Gaylord, a.k.a. B.B. Pelletier

Today is the Memorial Day holiday in the U.S. It’s the day we honor those who have given the ultimate sacrifice to defend our nation. Edith and I would like to join the rest of the country in remembering all these heroes from the Revolutionary War down to today.

This report covers:

• Technology advances as time passes.
• Not all guns changed over time.
• What about 88-gram cartridges?
• How does a charged gun suffer?
• How long can a CO2 gun be left charged?
• Can you leave a CO2 gun charged?

I’m writing this report for my good friends at Pyramyd Air. They get questions all the time about this topic, and they wanted me to discuss the whole story. It’s long, so sit back and enjoy it.

Gas gun technology advances as time passes
In this case, the technology refers to both the design and the materials. In the 1940s, Crosman made CO2 guns that were either charged from a separate bulk gas tank or else the bulk tank was attached directly to the airgun. The gas flow in these guns was very direct — from the tank through the valve and out the barrel.

Crosman 116 pistol and bulk tank
The Crosman 116 bulk-fill gas pistol was based on 1940s technology. Gas flow was simple and direct.

The seals in these guns were an early form of synthetic material that hardened and failed over time. But in recent years, all the vintage seals for these guns have been reproduced in modern synthetics that have a much longer shelf life and even longer operational lives. When a vintage CO2 gun is fixed today, you can expect it to last a very long time. A gun that might have leaked after 20 years of service in the 1950/60s can be resealed today and not leak again for the next 40 years because of the advances in materials.

In the 1960s and after, the design technology changed. The gas flow in these guns was not always as direct as it had been in the earlier guns. Airgun manufacturers were now making lookalike guns, and they were being constrained to put the CO2 cartridge in certain places such as the grip, where the gas might have to flow for some distance to get to the breech. Small metal pipes were used in some gas guns to transport the gas from where the cartridge was pierced to where the gas was needed. These pipes could not stand up to the pressure of a constant charge, and it was best to leave them discharged until you wanted to shoot the gun. This marked the start of gas guns that could not be left charged.

Another change was the invention of the magazine that also contained the gun’s firing valve. All the seals were in that tiny unit on top of what looked like a conventional pistol magazine. In these guns, the small flat end of the CO2 cartridge was pressed tight against what’s known as a face seal by some kind of tensioning mechanism in the bottom of the grip. When the cartridge was pressed flat, the end seal stopped gas from flowing out around the end of the cartridge; and it only flowed straight into the small firing chamber. The valve held this chamber closed until the action of the hammer opened it with force, allowing some of the CO2 gas to escape.

Makarov Ultra magazine
The entire valve of the Makarov Ultra is contained inside the magazine’s silver top.

Face seals usually work quite well, but there are some things about them that you have to know. One is their thinness. If they’re twisted while the CO2 cartridge is pressed against them, they can tear. If that happens, they’ll leak. This is a good reason to always use a drop of Crosman Pellgunoil on the tip of each new cartridge before it’s pierced.

Another thing you have to know is the length of the CO2 cartridge. If the cartridge is too short, the flat spot may not press tight enough against the face seal even when the tensioner is adjusted as far as it will go. That lets the gas leak out because the face seal cannot do its job. The solution for this is to try a different brand of CO2 cartridge.

Not all guns changed
As the technology changed, all gas guns did not change to use the latest designs and materials. The cheaper guns did go the way of face seals, gas tubes and lookalike designs; but there were more expensive gas guns costing hundreds of dollars that continued to rely on the older designs from the early years. These employed the very latest in materials in these designs. I’m referring to the gas guns used for formal target shooting. These airguns will hold gas for years without a problem because they are designed to.

What about 88-gram CO2 cartridges?
This question always comes up. While a gun that uses a 12-gram cartridge may shoot 50 or 60 times per cartridge, guns that use the much larger 88-gram cartridges can shoot hundreds of shots before running out of gas.

Walther 88-gram CO2 cartridge
The 88-gram CO2 cartridge is much larger than the conventional 12-gram cartridge. It contains much more CO2 gas, and, as a result, some thought has to be given to when it is used.

Should you remove an 88-gram cartridge after your shooting is done? In recent times, Crosman made a special adapter for their 1077 repeater (among other guns) to accept an 88-gram cartridge. That adapter has a valve that allows you to turn off the gas. The cartridge can remain on the gun, but there’s no gas flowing to the valve. I’ve had my 1077 with this adapter charged this way for several years.

Crosman 1077 CO2 rifle
Crosman’s 1077 repeating pellet rifle was made for a single 12-gram CO2 cartridge. Crosman used to sell an adapter that allowed the use of 88-gram cartridges.

Crosman 1077 gas system detail
The Crosman AirSource adapter shown here allowed the use of 88-gram cartridges. The knurled knob at the bottom of the vertical tube allows the gas to be turned on and off. This gun still has gas after being stored for 3 years!

Not all airguns that use 88-gram cartridges have a valve to turn the gas off. Shooters who use the 88-gram cartridges costing several dollars apiece must consider the shooting they are about to do to determine the probable number of shots that will be fired because some guns may suffer if left pressurized. If you plan on removing a 300-shot cartridge, better to do it after 275 shots have been fired, rather than only 25 shots. That would be like opening a $200 bottle of champaign so a friend could have a sip.

How does a charged airgun suffer?
A couple years ago, I asked Ed Schultz, Crosman’s top engineer, what damage is done when a CO2 gun is left charged. He told me that some of the modern seal materials can take a set if left pressurized too long. This was the first time I’d ever heard that; but since Ed is in charge of making the guns, I have to accept that it’s true.

There’s a second reason why the gun manufacturers don’t want their guns left charged, but they will never mention it: Liability. You see, a CO2 gun can shoot anything that’s in its barrel. It doesn’t have to be BBs or pellets. So children and irresponsible people can load things into a gun and shoot them even if they don’t have a supply of the correct ammunition. For this reason, a charged CO2 gun is a loaded gun.

How long can CO2 guns be left charged?
This is where the question gets personal. There are owners who obey the letter of the instructions and see it necessary to remove the cartridge within 5 minutes of shooting. If they planned on shooting again tomorrow, they would still remove the cartridge today.

Then, there are the more broad-minded owners who believe that they should remove the cartridges only when they think they’ve finished shooting the gun for a longer time. These are the people who will leave a cartridge installed for a week of shooting. I tend to agree with this group. But, sometimes, they forget what they’re doing and the cartridge never comes out.

The manuals are vague on this point, and I wouldn’t expect a firm answer from an airgun company, either. They have to defend themselves in court for whatever irresponsible actions are taken by those who use their products, so they can’t afford to give them any basis for a lawsuit.

I’ve left my modern CO2 guns charged for years, and eventually they all seem to leak down. Some will hold for more than a year, but eventually they all do seem to leak down.

My vintage CO2 guns, on the other hand, are always charged and never leak. They are like PCP guns, in that respect.

Can you leave a CO2 gun charged?
All of this brings us back to the original question — can CO2 guns be left charged? The answer is sometimes “yes” and other times “no.” It depends on the design of the gun in question.

These days, I tell people to follow the instructions in the manual but not to be anal about it. They can leave a gun charged overnight and even for several days; but before it’s put away, if the instructions tell you to remove the cartridge, that’s what you should do.