@Maiphut Yeah, the worst part was the way the motor pinion gear chewed through the power wiring at the base of the gearbox… so dangerous. 
@BME an LDX box would be the obvious choice, they’re made by LDT. But pretty much any V2 should go in. I transplanted an orange CYMA box into a 416D fairly easily. 
Not a huge fan of ball bearings in these things… but overall the box looks okay. Cheap at that price too.
Not certain if your anbi fire select will be problem free with it but who knows?
What gearbox would you reccomend.?
Or maybe, one of these…
they are on sale.
Hmm, programmable…
Maybe, put one of these, into the hollow, full 3d printed Robocop kit, and set it to 3 round burst…!!!
No idea haven’t used that one. Has no mag wiring by the looks. Nozzle is airsoft.
I’m looking at this one right now…
Wow… what a box… Golden Eagle V2, $175 at Oz Gel & Tactical. Nice! 
Same box that comes in the GE MP5
Yes feel free to use and distribute the discount code. As I remember, the discount is evergreen (reusable). Just to avoid self-promotion on my own, i have not share any discount in public posts but you are more than welcome to share anytime anywhere and to anyone
I’ve heard there’s issues with the FCU on those and they’re nearly impossible to replace.
They’ve been on sale for some time now, think they were the previous version to what’s used in the current batch or something like that.
Had looked at those in the past and had a number of ppl tell me otherwise.
The red LDT box is what was in some the full metal MP5’s too so that’s pretty much a guarantee fit.
Thank you, @AKgelblaster …
I did not want to publicly disclose a code, on your behalf.
Im sure people here will appreciate it.
I used the discount, on the Sten, i paid for this morning.!!
Cant wait to get it.!
Yea the red box is the advanced with the BR mosfet (is it by magnet instead of optics )
My thoughts, are this…
wait till monday, and see how @Wombat’s review goes.
If the JM is around the 220 mark…thats probably about as good as these will get, without too much work…
If thats the case, maybe just chase some airseals on the existing box, experiment with different gels, and have it sit around the 230-240 mark…
Otherwise, its go the whole hog, and do a new gearbox transplant.
Even then, 270-280 is probably the max, you’ll get out of these…
Good enough, for CQB…
Here’s my two cents
I figure if you’re not going to run it hard all the time springing for a higher quality box is a bit of a waste. War Interest boxes are pretty crappy but they can be improved.
Pull the WI box, shim the metal gears properly ( they sound like they need it ), throw on an alloy nozzle, cyl head and piston head, back it all up with an M90 spring. Fix all the niggly WI foibles while it’s apart.
Should give you about 280FPS if it’s anything like my 416D.
It’s only bench time, and that’s free… parts won’t cost much either.
But I do understand your search for perfection. 
If it were me I would go for an ldx expert, but I like building gearboxes from empty shells. Most I would recommend a ldx basic or advanced.
I does depend on the terminal block, I remember buying a ldx expert copy (might have been X-Force one) and the terminal block did not have provisions for mp5 only gen8 style. That was probably a year or more ago though.
As far as I have seen so far all actual ldx and some of the clones had mp5 capable terminal block.
Definitely wouldn’t touch and aps box, especially the mosfet versions as they can only be fixed with unobtainable aps mosfets.
You will have to open any ldx up and change wiring to front, mag terminals to mp5 springs, selector plate, trigger, and a 50% cylinder. So it is a bit of work.
The front wired mp5s can be a real prick at times. I wish ldt made the wiring hole bigger, or at least easier to feed through.
I’ll add this small point, it may be of interest to some…
One other thing, you can do with the LDT, is unscrew the very front of the barrel tip, and remove it.
I like this super short / compact look.
It really makes it look like something compact, that you’d find up the front of a tank…
I dont know if the JM can do this…
The barrel looses a little bit of stabilisation with the tip off, but not too bad…
I had a bit more a muck around today…
FPS was variable, on the pinkies ( albeit older ones), 180-225 fps…though i did see a few 250’s. That’s on a new M100 spring.
ROF was around 1100 r/min, as one would expect.
The gearbox is louder, the older shell unit is quieter, and running around 260fps.
If the existing gearbox could be worked to get to around that mark, consistently, i’d be pretty happy.
Looks more authentic K without the muzzle tri lug
Wonder if a Cyma sling loop end plate would fit 
CYMA MP5 AEG series Rear Sling Cover with Pin (Black) - Airsoft Tiger111hk - Welcome - English
iirc you mentioned it had a hole there or something. Would finish the look if it did fit.
I thought when I was looking at that back plate the other day that it would be neat to put the strap loop from the stubby Kriss Vector plug into it. It screws out of the nylon threaded plug so uber easy to fit.
If removing the tri-lug outer barrel’s made the IB a bit wobbly it wouldn’t be hard to make a short something up to really stabilize it and make the front end look a little more finished.
@BME would you like me to clear some space on the bench so you can get down and dirty with your W.I. gearbox? 
Sure…why not, if your offering…!!
I’ll bring a burton bar, for sustenance…!!
I’m guessing the gel shop , up the road from you, has all the parts we’d need.?
Yep, of course… we can spend some time getting your WI up to speed. once the boxes are sorted it’s usually an air seal issue at the t piece with those.
Oz Gel does have a lot of parts, but he’s only a small retailer so not everything brand specific. When I do a box up I usually have to order some from other sellers or get them off ebay.
I like his style though… I went in yesterday to see if he had any 370 motors (the magic smoke came out of the MP7 ), he spent ten minutes rumaging through a drawer of discards, threw an old gearbox from a Ming Ping Ho something or other and a screwdriver at me and said “Go for it”. Told me I could keep the whole POS box…
I opted to take the 370 and left the POS box with him, naturally…
