Bolt Airsoft is a relatively new manufacturer who specializes in Recoil AEGs, and one of their latest is the B4 SOPMOD.
Featuring a specialized V2 gearbox with a buffer tube located recoil weight, this thing kicks like a mule but still allows you to use standard AEG magazines and upgrades. It’s even rear wired, so you can change up the front end as wanted.
Booligan reviewed this gun here: http://www.booliganairsoft.com/2013/09/bolt-airsoft-b4-sopmod-recoil-aeg.html
Be sure to check it out if you’re interested in an electric gun with a little kick! Check them out at www.bolt.tw