Props to Talon for his effort to write in french
Not too sure about the other posts that followed though :P
Papiloran; Recoil is not about "vibration", this kind of solution wouldn't work at all.
Danke's link show what's the closest to having recoil on an AEG for now. However I've heard about ERG (Electric Recoil Gun) hitting the market, but I know nothing about these