Despite what some people say JG’s they are great guns, even if left stock. I’ve owned four of them 2 M4s and 2 G36s, and have worked on more than a few dozen. The older JG’s were just; ok (pre 2008). Now with JG’s enhanced gearboxes and stock IRLB3034 MOSFETs they’re seceding the standard for their price range let along some higher end AEG’s as well. IMO much better value than SRC/TSD and G&G and CA sport line.
The enhanced 2010 and newer JG gearboxes feature, Metal tooth piston, ball bearing piston head, 7mm ball bearing gearboxes and Metal springs. The standard JGs are shooting 350-370 FPS out of the box (depending on the type of the gun) and the enhanced versions are coming in at 390-440 FPS (

) (depending on the type of the gun). both the enhanced and normal JG guns come with good compression but I’ll agree with the above mentioned “replace the barrel, hop-up nub and bucking”, as JG’s are pretty inaccurate out of the box.
The blue “M-42” High power motor that come stock, which give JG’s the highest ROF (Rate Of Fire) out of the box for mid priced AEGs. The blue “M-42” features very strong magnets although not as strong as the SRC high torque but the JG M-42 produces a higher ROF. I haven’t been able to compare the red “m-93” ultra high torque motor but according to this
video and by playing it through Audacity the red “m-93” and blue “M-42” motors are both 20 RPS (rounds per second) with the battery he is using although I want to test this for myself to confirm.
I’ve owned many sets of JG gears both the standard set (M-58 ) and the enhanced (M-87, with internal bearing on the bevel gear and built-in sector gear chip). Both sets of these gears I’ve tested to at least 180,000 rounds at 370FPS @ 35 RPS and 390 PFS @ 25 RPS. Not only are these gears quite (I hate noisy gears!) but they can be had for around $15-$25 a set on ebay! Certainly JG gears don’t last as long as ICS or VFC gears (both of which I’ve tested to 200,000 rounds (VFC gears I’m still testing and are at 280,000 and still counting!!

) at 25+ RPS @ 370 FPS and above) but they certainly last longer than many other brands in their price range and for how much they cost, it’s a bargain!
There's a difference between a person who has a screwdriver and a person who knows what they are doing.