I have had seals become porous and absorb CO2 in internal blister-like deformations from which it would eventually be released. But I was taught at school that carbon dioxide was an inert gas, so I assumed that was due to a deterioration of the seal material that would have happened with any compressed gas
Having gone away and done a little research, I stand humbly corrected
Thank you, Master Lawrie
My experience: Umarex Beretta 92FS, 8 years old.
Used mainly in winter season, so can sit for several months unused.
Never left bulbs in it.
First 7 years I used Umarex bulbs. Never missed a beat. Always a drop of Pellgun on the tip of each bulb.
Easily shoots 2 mag's worth into 1/2' - 3/4" group at 6 metres, unrested. To mix units...
Last season I changed to Crosman bulbs - which appear to have some oil in them. NOT the Walther 'maintenance' bulbs which are for occasional use.
Got gun out a month or so back, bulb in, not working. Opened underlever and CO2 escaped, so bulb WAS pierced. Tried with several bulbs - both Crosman and Umarex. Maybe one bulb in 5 might work, but missed shots occurred.
Valve clearly sticking.
Flushed it, around 300 shots through it, and gun is now 100% reliable again with Umarex bulbs.
So, for me, Crosman bulbs will now be relegated to occasional (maybe 1 in 10) usage...
Umarexs don't like or need Pellgun oil
There Ive said it.