I'd just pickup a JG M4 from one of the member here (Very helpful guy).

This is my first AEG and I will take it apart and learn from it. Some of the part I would like to identify.
Here what I've done so far:
and I will paint the receiver tonight:
Can anyone give me suggestion to take the barrel nut off (Real tight) !!
Does any one know what motor this is? It says "Golden Eagle" on the sticker.
But it doesn't have very strong silver magnet.
Gearbox with SB marking (pretty sure its JG), but SB marking usually found in Black JG V2. Can some one tell me if this gearbox reinforced or not (Any relationship with the black SB marking JG V2)?
This Gearbox has metal gear inside and solid metal bushing. (Will take it apart apart later today or tomorrow to take more pics)
Also, those hex screws on the gearbox is lose when I take it out from the lower body, one of them was only half way in the threads (Can turn by hand).
Is it a common problem with JG V2? This gun choroned 360FPS, is it safe to put M120 spring in this gear box?
That's it for now guys!!
Thanks