Is Your CO2 Airgun Leaking? Here’s How to Fix the Hiss
There is nothing more frustrating than loading a fresh CO2 cartridge into your favorite air pistol, tightening the screw, and hearing that dreaded “psssssst.” A leaking CO2 gun isn’t just a waste of money—it’s a performance killer. If the gas is escaping, your muzzle velocity drops, your accuracy suffers, and you’ll find yourself out of air before you’ve even finished a single magazine.
The good news? Most leaks are easy to diagnose and even easier to fix at home.
1. Identify the Source
Before you grab the toolkit, you need to know where the air is coming from. Most leaks happen in one of two places:
- The Piercing Assembly: If you hear the leak immediately after inserting a new cartridge, it’s likely the seal where the tip of the CO2 bulb meets the gun.
- The Valve/Barrel: If the gun is gassing out through the barrel or the internal mechanism, you have an internal valve issue.
2. The #1 Culprit: The O-Ring
In 90% of cases, a leak is caused by a dry, cracked, or compressed O-ring. CO2 is incredibly cold; as it releases, it freezes the rubber seals, causing them to shrink and eventually brittle.
The Solution: Pellgunoil
Never load a CO2 cartridge “dry.” Placing a single drop of non-detergent silicone oil (like Crosman Pellgunoil) on the tip of every second or third powerlet will keep your seals supple and airtight.
Pro Tip: Avoid using WD-40 or petroleum-based oils. These can actually degrade and “eat” the rubber seals over time, making the leak permanent.
3. Don’t Over-Tighten
A common mistake is “cranking” the piercing screw as hard as possible to stop a hiss. This actually crushes the seal, creating a permanent indentation that will never hold air again.
- The Fix: Tighten until you hear the pierce, then give it a quick 1/4 turn to snug it up. If it still leaks, the seal is likely already damaged and needs replacement.
4. Storage Habits
One of the fastest ways to ruin a CO2 gun is to leave a full or half-full cartridge in the gun for weeks at a time. The constant pressure keeps the seals compressed, leading to “seal set,” where the rubber loses its ability to bounce back.
- The Fix: If you’re done shooting for the day, remove the cartridge.
When to Call the Pros
If you’ve oiled the seals and tried a fresh cartridge, but the gun is still leaking from the internal valve or the trigger housing, you might have a blown internal gasket or a debris-clogged valve. Unless you’re comfortable with a complete teardown and have a schematic handy, this is the time to visit a local airgun smith, or give the shootfish Co2 sealpro a try.
The shootfish sealpro fits on the Co2 cartridge and provides an instant leak fix. It works in conjunction with the existing seal, and there is no need to use any oil, use it dry. Not only does it fix leaks instantly, it allows the gas to be left in the gun with little or no leakage.
