I just recieved my KWA Glock 18C from airsoftgi today. It's the full upgrade one, metal slide, upgraded recoil spring, high-flow valve, all that good stuff. So naturally, as soon as I opened it, I took outside, filled the mag with Green gas, dropped the included BBs in the mag, and emptied the mag on full auto. (Which was very nice, btw) I thought "Wow, that was cool, let's do that again!" refilled the mag with BBs, cocked it, pulled the trigger (full auto again), it gets 2 shots out, then stops. I dropped the mag out and tried to pull the slide back, (assuming that a BB got jammed) but it's stuck. It only moves back maybe a quarter inch, but if I pull the tabs down to disassemble it, it slides forward maybe an inch, then stops. What do I do?