If I'm not mistaken... I'd say under the bottom plate of the magazine <face palm>. the KWA Glocks are the same way. Slide the bottom of the mag off about half way to reveal the gas intake nozzle. I think those are GBB's, so of course the gas would be held in the magazine... at least, for me, it's common sense to check there
also, quick question, why do people refer to the magazines as clips? I've never understood the term :-k