wertyq
First order of business for storage, all safetys in the SAFE position. Trigger locks if you have em. Locked cabinet or Gun Safe even better! OK?
On the old Sheridans, always store em with at least one pump. It keeps the seal pressed against the seatand keeps dirt out.Keep the action Uncocked, to save the hammer spring.
I keep my new Cartrige Valve type 392 stored with one or two pumps in the gun, and with the bolt (Hammer spring), just lifted till it "clicks" allowing the seals to seat.
I store my little 760 with a pump or two in the gun,hammer spring uncocked.
Co2 is a little trickier! Some guns (like the modified Co2 Hot-Rods from Mac-1), are supposed to be stored charged, but uncocked to spare the hammer spring.
Crosman says store their guns uncharged, uncocked.
I think you could be pretty safe charging your manually cocking, multi-pump pneumatics with one pump of air in them.
(*Safety Note here! Except for Self-Cocking actions! Leave Self-Cocking actions UNCHARGED!) Examples are the old Crosman 760 and some Crosman Model 140 and 1400 rifles and some models of Crosman pump pistols.
Single Stroke Pneumatic guns should be stored UNCOCKED and UNCHARGED, since one pump is a FULL charge, and might cut the seal if left for long periods.
Storage procedures are a can of worms! These suggestions are just a rule of thumb that I follow from the Owners Manuals I have on my own airguns. The procedures are pretty generic though.
It's always best to contact the manufacturer and attempt to obtain a copy of the Owners Manual for their recommended safety procedures.I would suggest that you try and contact the Manufacturer, the Owners manual copys are usually free.
HTH,
ZVP