I own both the plastic JG HK416 V1 (the first gen that came out late 2007) and the Second Gen (which came out 3rd quarter last year), thought I might do a quick review since I referred to this review when I first decided to get that JG. Conceivably someone out there who decide to get a JG HK416 will get here via google will find this useful.
Summary: JG HK416 has very drastic improvement over their gen 1:
1) RIS unit:
On the Gen 1 HK416s the RIS was secured with a pin and had serious wobble issues. The fix for this is of course using a piece of coke can metal which will decrease the wobble a lot, but it was still noticeable.. (The fix from this came from one of the experienced gunsmith on Airsoft New Zealand)
On the Gen 2 HK416s as seen above they use a new method, and now the gun is solid out of the box.
2) MOSFET unit:
GEN 2 HK416s now come with them.:
The motor is still the same, but notice that they have now used silver wiring
The motor is highly magnetized, and power the stock M125 spring without issue or sign of strain. I can't say for sure how good it is though.
Now for the highlights which will make some people shit themselves:
On the Gen 1 HK416 (persumably JG System Mechbox Gen 1 as well) they use a typical Chinese TM piston clone with last teeth reinforced
On Gen 2 - fill metal teeth piston, a replica of the Systema red piston I believe.
Air-sealing is perfect out of the box - even with grease wiped off. (which is a common trait of ACM guns wanting to improve air-sealing by chucking grease near the o-ring.) Though the same can be said for the Gen 1 HK416 piston.
2) Mechbox shell
On the Gen 1 HK416 the mechbox shell is Marui Ver.2 clone with full metal.
On the Gen 2 HK416 I believe these are the Systema reinforced mechbox clone. They are definitely the same sort of mechbox the G&P stuff is based on.
Also notice the metal bushings that now come stock standard (in the past you either have to settle for nylon bushings and pray for the best, or get the modifed JG metal bushings from WGC shop
Lastly, see how clean the mechbox is? Unlike most other ACM clones, this mechbox does not suffer from over-greasing.
3) The mechbox in full
You can see
1) Their gears are completely different than what you see in any ACM guns. These gears I believe are a clone of the Systema gears.
2) Notice the silver wiring
3) Notice that the cut-off lever didn't pop out? Used to be a nightmare in the Gen 1 HK416
4) Lastly - noticed everything is good to go before you put on the mechbox shell and lock it up? Everything just sits nice and still in there.
Not included in photos
1) Drastic hop-up unit design changes: On Gen 1 HK416 they use a 2 piece hop-up unit which is a nightmare for air-sealing especially if you broke the stock hop-up unit and try a new one.
On a Gen 2, they use a 1 piece hop-up unit which "interfaces" with the cylinder head, giving very good airsealing
2) shimming - shimming was clsoe to perfect out of the box, I adjusted the spur gear shimming and also the bevel gear, but if you chose to run this mechbox without alteration you should be fine
Performance: Chorono at 405-410 FPS with a Xcortech X3200.
This is probably now the best HK416 in the market - unless you are an argumentative VFC owner, in which case you'll argue it's the second best but best bang for the buck
. They are some minute casting marks on the gun body, and the body material feels like cast-iron (so a tad heavy than the aluminium stuff VFC is made of, but certainly no Dboys pot-metal crapiness) but the internals of the JG HK416 is made purely of win.
My HK416 with G&G SCAR QD silencer flashhider + Dboys NWSC Crane Stock (though modded to be extra firm) + Magpul PTS MOE grip.