Regarding removing the cylinder ... I only use the small ones in pistols. I always use them to almost empty by firing pelets into my pellet trap .. after target use I put a few more interesting targets up ... old plastic party whizz things are fine. Then when the point comes when it is best to remove cyclinder or risk a stuck pellet (after 60 shots with a S7W, more with a CP88) I now try to vent through the valve system by pushing the hammer to release the valve. I used to simply release the gas cyclinder retaining mechanism and let the gas escape through the butt, but I was advised (via this forum???) to use the hammer method as it causes less harm to the cyclinder seals.
Cheers, Phil