@BME same screw? 
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? 
Yeah, it did…
As per my original thread…it only did 190 fps OOTB.
I pulled it apart…and the spring retainer was out…
No biggy, I was putting in a new spring anyway.
M100 in, and it was doing 315 fps…for awhile.
Then, after some time fps dropped to 180ish again.
This was the due to the lower quality factory seals shrinking ( I didn’t pull the box apart initially).
DocRok gave it the medicine, new seals on the piston and cylinder head, new piston, piston head…and viola 330 fps constant.
It seem the standard orings aren’t high quality, so best to replace them…
A very minor price to pay, to get a good result in the end…
Agreed… worth the fettling.
When I tested compression with the factory o ring on the piston head, it was zero… absolutely no seal with that o ring at all. In fact, the diameter of the o ring was about half a millimetre shy of the cylinder bore.
Must be how they’re complying with the low FPS restrictions in China, which is good news for us. Change a few seals and boomshanka! Good performance again. 
At least they’re not driling holes in t pieces and such to lower the FPS… 
After a day of trialing different combos of piston springs and nozzles, arrived at the final result.
New M100 spring, T238 piston and piston head with spring bearing (holes opened up about a millimetre), stock nylon nozzle (gave a higher reading than the upgrade nozzle, even when it was spaced out with an o ring).
Consistent low 300s with iHobby ultra hards
Consistent 290s with Armour Tech greens
Good enough.
@BME it would seem your upgrade cylinder head is making the difference in FPS
Yeah the Cyma G36c is def gaining a bit of popularity in China. Great value for such a solid nylon build. Biggest issue would be the stock inner barrel being too short to put a hopup on, so the first thing they do is put in a longer barrel.
To be honest, I’m not sure ROK upgraded the cylinder head…
It might still be stock…with a new oring…
Chinese manufacturing tolerances…!
Colour me dumb shit… 
I’ve been putting this piece in and out every teardown, scratched my nut over it plenty, it doesn’t look like it does anything when you’re looking at it in pieces.
Bugger me… it’s mag prime.
What threw me was Rok’s GBN review earlier where he mentioned CYMA dropped the ball when they left prime off… I kinda figured it didn’t have it too.
It pays to read the idiot sheet that comes with it. 
They call that expectation bias…
Whoops, me too…
@BME so I’m not the only one who missed it? I’m gonna asume @RokSolid did too.
Have to say after a day of manually filling mag feed tubes for test firing, discovering this had mag prime was like winning lotto. 
The G36C has risen even higher in my estimations now. Damn solid blaster and a joy to work on.
@Martin I can see why they’re popular in China… and yeah, it’s a shame most manufacturers don’t allow enough inner barrel to fit a hop up.
What’s wrong with you guys, it has mag prime written all over it
Not Surprise bonus is always good
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