Not a purchase on my part, but new to me nonetheless.
A huge shout out to @BME and @RokSolid for very generously organising delivery of a very sexy CYMA/Jund G36… with upgrade parts. 
I’m still a bit shell shocked, a total surprise out of the blue and for the life of me I still can’t work out what I’ve done to deserve such consideration, but it is greatly appreciated. 
Thank you, Beemer & Rok… Legends, both of you. 
Just picked up one myself and it’s a great shooter stock. I’ll do the o-rings, piston and spring at some point but for CQB I’m super happy given the price. For rifles with a mostly synthetic look, the Cymas are such great value. Not sure I’d be happy with their AK but the G36c looks great and an FN2000, Famas, etc would be sick.
Yeah, CYMA have definitely upped their game with their build quality lately. Very solid.
Hitting a little low on the chrono at around 200FPS but considering Chinese restrictions these days, not surprising. A longer inner barrel and a hop up, a few upgrade airseal parts and it’ll be an absolute pearler.
Looking forward to getting stuck into this V3 box.
seems to be the go with the new Cymas…
Average orings, OOTB.
But, it takes very little to get them singing.
For my G36, we kept the original barrel, upgraded orings, M100 spring and maybe a new piston? Cant remember, without referring back.
Then, its a solid 330 fps blaster…out of a M100…!!
put in a M90, get 300 fps and reliability for a very long time…!
Sub $200, you cant beat it…!!
RokSolid
Ealdorman
1
Had a play with @BME 's G36c.
Seems the cylinder head and piston head o-rings had shrunk. I’m not thrilled to see it but while replacing them, I also replaced the piston and piston head.
Now this is the first time I have used the new T238 Pro piston, I have heard they are tough, and they do look meaty, the rack is near impossible to remove, and the piston head I have used a few of.
Only replaced the piston as the stock one has only a single metal tooth… fine for bb slingers but for gel full auto use, piece of mind is to have a full metal rack!
And the piston head was replaced as the stock one is not compatible with other pistons without work.
In all. Two o-rings, piston. Piston head, BME 's m100… that’s it. Little clean and grease and oil.
And the results?
Decent numbers I reckon!
Not much point trying to reshim unless swap to slim bushes… stuff all room!
As for a V3 box. Pretty good to work on. The trigger and trigger rocker stayed put for the whole operation, anti reverse behaved, and apart from trying 3 other pistons and heads first was pretty quick.
Let’s just say… I’m ordering more of these t238 pistons for any future cyma as they fit and worked well, the rell test is how long they last, but I am prepared to swap it out if it gives trouble because I don’t like using parts I have tested myself prior!
There you go…save looking it up…!
@RokSolid you just know I’ve voided my warranty already. 
When I pulled the box, I noticed the spring retainer hadn’t been locked in place 
Easy fix but does require box removal. Funny we’d be talking about spinning screws a while back though. One of the three screws that hold the t piece assembly into the receiver was nut spinning, couldn’t get the inner barrel out to remove the gearbox.
Had to dremel the head of the screw off with a diamond point to get it out. Even when it was out that nut would not budge on what was left of the screw. Must have used gorilla strength loctite back at the CYMA factory. 
Whacked in an M90 spring and it’s up to about 250FPS now… box is coming out again this arvee for the good gear for improved airseal.
Found this disassembly video on Youtube, in Chinese but it’s a handy visual guide for these G36 blasters if you’re not confident.
Good times!
Thats two for two…!!
Same as mine…!!!
Must have been assembled, on the same day, by the same person as mine…hung over or whatever…!!
Wait… your spring retainer was popping out all the time?
New full rack piston, piston head, nozzle, piston o ring and cylinder head o ring went into the G36 this arvee, I think an M90 spring too.
Also disabled blowback which has made reassembly that much easier and was necessary anyway with the new piston.
I agree with Rok that the stock cylinder head lets these down bigtime. I’ll look into a replacement when I do the inner barrel… piston o ring was way small, zero compression. The cylinder head o ring likewise, but all easy to replace and shouldn’t put anyone off getting one.
I also agree that they’re a well behaved V3, everything pretty much stays in place and they’re a fun box to work on. Pull one of these G36s down once or twice and you get pretty quick at it. Lots of steps but mostly takedown pins and six screws so dead easy. Stock OOTB before upgrade parts I was getting about 190FPS, after upgrades…
280FPS average, a decent result, consistent with an M90 and very happy with it. I’ve got a feeling it’ll jump another 15 to 20 or so with a better cylinder head.
Good stuff…!!
Grouping pretty good, at that fps.??
At 330, mine is mostly good, but getting a few fliers.
If you should feel so inclined, I would be curious to see what a M100 would do, in your setup.
That would show the difference in the cylinder head, which is the main difference in my setup…
Only if you’re keen…!
Accuracy’s pretty good… it’s now running a hop up, and I’ve always put 270-280FPS as my sweet spot for accuracy
Hard to say what it’s grouping but it’ll hit a Milo tin lid 18 metres away about 3 out of 5 shots. Then the wind blows.
At CQB ranges (5 - 10 mtrs) it’s pretty much bang on.
Some nice work the @Friendly_Fire
Bit disappointed in it for me, as I tested it before shipping it and had a good 250-260fps, no sign of the retainer being out.
The real beauty is they are so quick to disassemble. I see why many airsoft fields use them as rentals. If you had a spare gearbox they would be back up an running in minutes!
I keep thinking I need to keep one for myself!
It’s gotta be one dodgy factory assembler…
With the 4 point retention system, if it’s done up right…it’s staying in place.
If it’s pushed in and given a small turn, and not locked in at all…
It won’t take long to vibrate free…
Thankfully, it has the backing plate to catch it…
190-200 fps seems to be the result, from an unsprung spring…
A good clue to what has happened.!
what hop up are you running?
The one in the photo is similar to one of these…
Rizer alloy adjustable hop up -slim. X-Force sell them.
But to run it in the CYMA you have to either fit a longer inner barrel and a different flash hider or modify the outer barrel assembly and bore out the stock flash hider to 11mm to fit the hopup.
I happen to love the look of the original and I want to keep this stubby so I modded. I’ve been known to do weird shit.
Ah, not to worry, Rok. All good, not too big a drama… and you very kindly included all the parts needed to fix it. 
That retainer probably disengaged during shipping, but I’m keeping an eye on it. While it was in the process of assembly and disassembly I noticed that it had popped out again. I’ll give it a bit of use today and see if it’s secure with the added pressure of the bigger spring.
It’s coming apart today again so I can loctite the cylinder head screw… ooooops!
Maybe slight differences in the depth of the slots in the moulded case, maybe the size of the four lugs on the pin itself. But if it pops out again I’ll fit a flat washer and screw into it. Might be worth monitoring it in case there is a factory fault.
@BME can you confirm that your spring retainer had popped out too? 
