1 - Buy an electric airsoft rifle
2 - cut out all the electronics except the trigger
3 - install the aimtrack in it, connecting it to the existing trigger wiring
4 - drill some holes in the gun and add a few more buttons for good measure
5 - wire them up to the aimtrak
6 - add some weights inside the gun until it feels right. You can buy lead in a coil at any fishing store, just spool it around inside the gun and slop some hot glue on it to keep it moving around
OR
1 - pay me a lot of money to do it for you
http://www.airsplat.com/Items/ER-NE-M83-B1.htmSome black paint and it could be beautiful
Google airsoft aeg + whatever shape gun you want.