I purchased this gun brand new from one of the advertised retailers on here. I've always loved the MP5 and wanted to pick up a one of the "cheaper" companies model to work on and upgrade. After seeing so many people bad mouth JG I figured I would buy one and check it out for myself.
Let's start with the packaging. To be honest it's not the most secure factory packaging I've seen. I prefer the gun to be in a styrofoam tray. In this case the gun sits in shallow carboard cut outs with just the two pieces of foam on the top.
Included in the package you get
-manual
-cleaning rod
-metal 200 round hi-cap
-200 0.2g bb's
-8.4v 1500mAh battery (shown in pic)
-wall wart charger that has our standard plugs (shown in pic)
Picking up the gun for the first time I was pleasantly surprised. No creaks/cracks coming from the plastic. I held the gun horizontal from the end of the stock and shook it and still nothing. The flash hider is huge and orange as you can see in the pic.
But wait..The manual shows us on page 15 that the flash hider can be removed by pulling out two pins and flipping up the lock lever.
What do we find under the huge flash hider but a normal metal MP5 flash hider. It also has a removable threaded front so you can easily attach silencers. Bonus for me. Wasn't expecting that.
Being a full stock model the battery compartment is in the stock. Nothing major to report here. It can take a full size 8.4v battery.
The motor is a long type. No markings on the motor , just all black can.
Added some pics of the mechbox. Not a ton of lube in the mechbox, one of the plastic bushings was out of place though when i took the gun apart (see second pic). Anti-reversal latch can be seen on desk in the pics.

I've chrono'ed the gun and it's averaging 360fps. It weighs in at 4.5lbs with battery. The real gun weighs in around 5.5lbs - 6.5lbs from what I've read. So it's heavy enough so you don't feel like you are carrying a total toy but not so heavy that it will wear you out.
One of the only flaws I have with the gun is the selector switch. It doesn't click nicely going from safe-semi-full. Sometimes there is a click, sometimes no click. I'll try to fix the problem when I take it apart at some point. From what I've read though this is a common problem.
The rear sight does spin easily as noted in other reviews. How ever there is an audible click when going from selection to selection.
Overall I'm happy with the gun. Trigger response seems to be decent. 360fps out of the box with 0.2g is respectable. The fit and finish of the parts is well done. No gaps or cracks to be found. The JG MP5-A4 is skirmishable out of the box and gives a solid base to upgrade from.
Final pic of my MP5 with mount and reflex scope.
Pros
-Price
-Everything you need included in box
-Solid feel/weight
-Good velocity out of the box
-Orange flash hider easily removable revealing threaded outer barrel
-Great base to upgrade/learn on
Cons
-Selector switch needs work, can be easily moved from safe - semi - full if not careful
-Velocity out of box is too strong for CQB games