First, the manufacturer’s suggestions are mostly based on liability issues related to leaving an unattended airgun “loaded”. A CO2 gun with a charged cylinder is dangerous, even if no pellets or BBs are in the gun, due to the significant muzzle blast (the blast alone can damage an eye or ear of an unsuspecting child or adult). An airgun with no CO2 cylinder in it is basically harmless. Therefore, the manufacturers almost always recommend removing the gas cylinder at the end of each shooting session.

For long-term storage (more than one month), my recommendation is to always remove the cylinder and to make sure the seals are kept lubricated (see recommendations below). CO2 cylinders all differ slightly in the shape of their tips and leaving a cylinder in a gun for a protracted period of time can leave an imprint in the seal. When a different cylinder is inserted, it might not seal properly due to the impression left by the previous cylinder. I’ve purchased numerous vintage airguns than have arrived with CO2 cylinders that appear to have been left in the gun for 10 or more years. Many of these guns are still charged with CO2 and shoot fine. However, when the old cylinder is replaced with a new one, most of these guns wind up leaking badly around the seal. For example, I recently bought a Crosman 38T (.22) that came with an old “bottle cap” style CO2 cylinder installed. Judging from the dirt and spider webs around the cylinder and grip it looked like the CO2 cylinder had been in the gun for 15 – 20 years. To my surprise, the old cylinder was still almost fully charged and the gun shot fine, clocking .22 pellets at over 300 fps. When all the gas was used up, I carefully removed the old cylinder and inserted a new one. When the new cylinder was pierced, all of the gas rushed out around the seal and no amount of Pellgun oil would stop the leak. The gun was shipped off to have new seals installed.

So, here are my recommended steps for preserving the longevity of the seals in CO2 airguns:

• Place a drop of Crosman Pellgun oil on the tip of EVERY new CO2 cylinder installed in an airgun.
• Do NOT leave a charged CO2 cylinder in an airgun for more than about a month.
• When removing a cylinder that still contains gas, slowly release the gas to avoid cooling the seals too much (better yet, just shoot the gun until all the gas is gone). A sudden release of gas can tear some seals.
• Do NOT over-tighten the CO2 cylinder in an airgun. Tighten it just enough to pierce the cylinder and seal it, but no more.
• If you have a CO2 airgun that leaks, put two drops of Crosman Pellgun oil in the cylinder seal area and let the gun sit for two hours. Then, insert a CO2 cylinder and shoot the gun to distribute lubricant to the internal seals. Remove the CO2 cylinder and put the gun aside for three or four days. About 40% of the time, you’ll find that the gun will not leak the next time you use it. If it does, it’s time for new seals.