[Non Credo]

Hey I just picked up HFC's T77, and I wasted all day giving a tree a new hole to breathe out of, still havent discharged all the mag's gas. Still running strong, and GBBs are not my area of expertise... Will leaving gas in the mag for long periods of time damage the mag? If I must discharge the gas, and dont want to spend forever loading, firing and reloading, how might I go about releasing said gas? fyi it uses green gas, (propane), and yeah, its a pretty awesome backup. Great gun for the price, ROF is insane, even on full auto still relatively accurate. Maybe 1 foot groups at 20 feet, (pretty good, I'd say, for something with like a 4 inch barrel) Ive got a bunch of other mags for it, so, doesnt matter that much if this one I've filled is damaged, but I'd like to know how to do this. I know theres the little gas valve on the top of the mag, but dont want to go into something not knowing what Im doing. halp pleaz