lol, my guns run off of green gas. Slide blows back on every shot, and all of my guns have high-flow valves installed, which really makes them recoil when you shoot. The gas charge is in the magazine, and one charge is good for about 75 shots, which is about 3 mags (they hold 25+1 BB's on average).
I also have two Automatic Electric guns" (or, AEG), which are both replica assault rifles... an m16 VN (Vietnam edition) and a M4A1 R.I.S (with full metal upgrade)
Aww yes.. I'll take some pics and post em
EDIT: I mean I have 12 AEG's, not 2 ;)