Safe storage of pneumatic airguns
by B.B. Pelletier
A couple questions have come in regarding the safe storage of pneumatics and whether they should be left with a pump of air in them. I have reviewed what I've written on this issue and it hasn't been thorough enough. Here's the full story.
I meant multi-pump pneumatics - and not all of them!
If a multi-pump has an impact-type valve, it needs to be stored with a pump of air in the reservoir. An impact-type valve has a hammer that knocks the valve off its seat, momentarily allowing the compressed air to escape. Owners' manuals used to tell you to leave a pump of air (or two) in the reservoir of a multi-pump pneumatic to keep both the inlet valve and the exhaust valve closed against foreign (airborne) contamination. An example of a gun that has an impact-type valve is the Sheridan Blue Streak.
Some multi-pump pneumatics, such as the Daisy 22SG, will not hold a pump of air unless the gun is first cocked. Therefore, to store those guns with air, you would also have to store them cocked - something I would never recommend! However, it is possible to uncock many of these guns (but not the 22SG!) after pumping them, so those could be stored with air in their reservoirs. The Sheridan Supergrade was a gun that had to be cocked before pumping and could be uncocked for storage. The Daisy 22SG has apparently been carefully designed to make it impossible to store with air in it - so don't try. Always follow the manufacturer's recommendation given in the owner's manual.
Another BIG exception
This is what prompted this posting. Haque, a reader from Indonesia, owns a Sharp Innova, and he asked about storing it with a pump of air. The trouble is that the Innova has a different type of valve mechanism. Instead of an impact valve, the Innova has a blow-off valve. Blow-off valves were created to end the problems of over-pumping pneumatic guns. Read about that in the Sept. 19, 2005, posting, Another oldie - Crosman 130. The Innova's trigger holds the exhaust valve shut. Whenever air is in the reservoir, this kind of airgun is cocked and ready to fire! There is no separate cocking action that needs to be taken. That makes for a very unsafe situation if you fill the gun with air to store it - not because you are storing a cocked gun (although you are), but because that type of valve is well-known to fail! Guns having blow-off valves can fire without the trigger being pulled! I've had it happen on numerous occasions with many different models of guns.
Fortunately, the guns with blow-off valves aren't very common, but the whole Sharp line has them. The giveaway to one of these blow-off valve pneumatics is that the trigger becomes harder to pull as the air pressure increases. DO NOT store them with air in them!
What about single-stroke pneumatics?
The manuals for most single-strokes say not to store the gun with air in it. We had a question about doing that with an IZH-46, and I know it covers that specific point in the owner's manual. What's at work here is safety and damage to the airgun.
To charge a single-stroke pneumatic, it must be cocked - and you never want to store a cocked gun! The design of the single-stroke mechanism introduces the possibility of damage to the gun if you leave it pressurized. In order to work, the seal must be flexible enough to expand and seal the compression tube. Being that flexible also means that storing it under pressure will soon cause it to extrude (be squeezed through the tiny spaces it seals) and fail. For this reason, the IZH-46 manual tells you not to leave the gun pressurized for extended periods.
Precharged guns such as the FX Black Widow and the Aeron B99 are always stored with air in them. They all have impact-type valves and benefit from having their inlet and exhaust valves closed against airborne contamination. The only time to take all the air out of them is when you ship them. Otherwise, leave them with at least a caretaker charge to keep the valves closed. There's no harm in leaving them filled to the max at all times.
I hope this clears up any questions you might have had about storing your pneumatic guns with or without air.