[coach]

Gas is stored in the mags. They are the primary source of leaking. But mags are serviceable and sealable. Leaking comes from failed seals/orings or damaged full or flow/rocket valves.

A leak in the gun would be more so that you broke something. Happens but much less likely than a mag leaking on you.

Closed bolt = brass cylinder inside the ejection port. You cannot see the mags feed lips or confirm if there is a round loaded or not.

Open bolt = no brass cylinder. System is much like that of a gbb pistol. Mag feeds lips are visible and you can quickly identify if a round is chambered.