He did post something about it on here, but not really officially.
Luckily he’s not too far away from me, so I kinda got ahead of the game. 
Yeah it’s a weird looking spring, pretty hard to tell from the pic, but the windings look thinner in the middle than on the ends! 
Saw a couple of blasters pop up on a discord but that was about it. Not that I really have the funds or room to add anything currently 
Very cool 
Looks like there’s gonna be a few lucky people carrying on @Bigmuthadrums Madman build legacies 
Got the correct head and nozzle installed in the CYMA. M100 spring and 330fps with stainless steel barrel with Uband hop-up. Still need a bit of tuning to get better distance. Accuracy is great - getting good results with Uband hop-up, which is like a Rizer with large side vents
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Funny thing that I found the CYMA M4 CQB’s were the very worst accurate blasters that I had ever purchased………And I had 17 of the fkn things, so I didn’t just get one or two “bad eggs” out of the whole CYMA/JUND production line 
In all fairness though, I only took apart and modified 3 of them for my own personal use, but still took a lot more work than any old Gen8/9/10, WELLS, ACR, UMP, MP5, AK or whatever other brand/make/model to get some decent performance and accuracy out of 
I still don’t understand why, because the CYMA M4 CQB was a great quality blaster compared with most others on the market, yet was something about them that really did my head in to simply achieve pretty basic accuracy out of them.
Think stock CYMA barrel length doesn’t match the cylinder porting. I’m getting good accuracy with unported cylinders, M100 springs, 370 - 390 x 7.7mm barrels and the Uband hop-up with the larger side porting. I was always able to get better accuracy with a Rizer with a 3/16" port on each side than with a AKA hop-up
Once I get this new build running accurately to 35m, going to retire the ACR and all the AUGs, except the CQB shorty
BTW - just punched 15 x 1" holes in a fan shroud using manual firewall punch . Elbow is so bad from the ratcheting not sure I could complete a game session with a blaster with a metal handguard
From memory the CYMA/JUND CQB’s had a 30cm barrel @ 7.5mm I.D. exactly the same as old Gen8/Gen9/10 blasters, yet had a 75-80% ported cylinder as standard?
The major difference that I found between the older Gen8/9/10 blasters and the later V2/V3’s was the nozzle size.
I was only able to achieve 430-450 FPS out of the old Nylon Gen8 Gearboxes due to their larger size nozzles, which were able to move a shitonne of airflow from the cylinder compared with the later models that had tiny Airsoft sized nozzles.
I did experiment with one of the CYMA/JUND models by retrofitting a 100% cylinder matched with a Gen8 sized cylinder head/nozzle…… but getting the right t-piece to match was the last process that I got up to when the WA Bans came into force, so never got the opportunity to finish that particular project 
Doing the basics of air sealing, shimming, barrel stabilisers etc etc didn’t really have any effect on the accuracy of the CYMA/JUND, so I had come to the conclusion that it must have been something to do with the Volume Ratio being way out of whack for the whole setup.
I loved the awesome little JUND Hop-ups that were included in the box, and found them quite efficient, even to the point of collecting quite a few extras and fitting them to other customers different brand/model blasters 
In saying this though, the accuracy of the CYMA/JUND was still shithouse with those hop-ups fitted, and yet on many different other model blasters they were awesome!
I definitely think that you are onto it regarding the 100% cylinder and barrel sizing, which is something that I wished to have the opportunity to explore further myself to improve the performance of such a great model blaster.
But it’s like everything in this hobby, no two blasters are the same and it takes a lot of experimenting and parts swapping to get the best results out of whatever is being worked on at the time
I think the main issue with the cyma cqb/mk18 is they are a bit under volume, the stock oring is almost pointless and the stock nozzle is pretty leaky.
I have a custom bista build with a cyma nylon box that is using the stock ported cylinder, but is correctly volumed with good sealing parts and has an inner barrel that is a bit shorter than the stock cyma (200-220mm from memory) it is decently accurate with a hopup.
I did at one point buy a “prop/model” cyma for $42… from an undisclosed “tac-cy” toy retailer. Amazingly the thing worked and only issue was it was doing about 140fps. I replaced all the internals for metal parts, with good sealing head/nozzle/orings, and using a suppressor extended the barrel out to 380mm, with a full cylinder an m100 was doing 350fps, pretty consistent and the accuracy with hopup was mediocre to okay… but I only tried it with armourtech yellows. sold it pretty quick to budget another project so didn’t really have time to persavere with it as I got a good offer on it. At the time I put it down to the non free floated handguard and barrel that wasn’t really very stable.
@DocBob I reckon you are onto it with the gen8 vs v2 style nozzles… my experience is that the gen8 size nozzle is easier to get a good seal and reliable feeding. The tappet design does make it harder to get consistent fps at higher rates of fire, upto 30 with short strong return spring and a few mm trimmed off the tappet plate is pretty easy to get right, over 30rps is a bit of a time and tappet plate consuming nightmare; but possible up to high 30rps.
The v2 size nozzle and tappet is easier to get high rps builds consistent, they also tend to be better with barrels that are too long (400mm+) than the gen8 size nozzle. They do tend to be a little fussier with feeding than the gen8 size nozzle though, I guess there is always trade offs.
My personal favourite is the SLR nozzle and tpiece. Something about it’s tappered pointed design allows a super good seal directly to the inner barrel, and feeding is very reliable. One of my absolute favourite blasters is a custom with a JG box, that uses an SLR nozzle and tpiece, it is very accurate, and always gets 340fps with it’s m100, even though it has a barrel of only 220mm. It is also a 13:1 build at just under 30rps, and the JG box uses a gen8 style tappet plate that has about 4mm trimmed off the tappet tail. It runs very consistent shot to shot fps too.
Thanks heaps for your reply of your own knowledge and experience with all of these different technical details
The tapered SLR/V2 style small diameter nozzles definitely gave much more surface area sealing than the blunt old Gen8 style nozzle rubber/t-piece “seats”.
I only achieved such high FPS through much modification to the Gen8 nozzle rubbers, t-piece/barrel contact surfaces and heavily modified tappet plate profiles, return spring pressures and timing adjustments to get absolute 100% high pressure nozzle air seals and feeding precision with only minimal standard RPS speeds to ensure high FPS performance.
Again, I never fully delved into the high RPS builds, as there’s always a compromise between FPS, feeding and accuracy when reaching for the skies on insane RPS.
Your comments about the CFM capabilities between the larger Gen8 and smaller V2/V3 nozzles both have their own specific strengths in each individual build for sure.
The larger Gen8 nozzles, built with 30-35cm barrels of specific different ID’s to fine tune the performance of 100% cylinders were the best results that I could ever achieve through hundreds of hours of building and testing……. still staying within the limits of standard RPS speeds.
They could be tuned to move a shitonne of precision CFM into the exact right barrel length/diameter, and could even tune in “air cushion braking” of the piston within the cylinder/head/nozzle to prevent piston head slap and provide a “long pressure feed” through the barrel to boost the length of time that air was being supplied behind the gels travelling through the barrel.
The smaller diameter V2/V3/SLR type nozzles could also be tuned to do the same thing, but it took much more work to achieve the same results as the old Gen8 build parameters.
Amazing example of the CYMA standard Blue nozzles, is that I would build a custom CYMA gearbox with aftermarket Alloy cylinder head with double o-ring alloy nozzles, and yet in testing, the stock blue plastic nozzle fitted to the aftermarket alloy cylinder head tube would actually achieve higher FPS and air sealing than the o-ringed aftermarket nozzle!
Totally agree with you on the fact that every single one of those 17 CYMA/JUND M4’s that I got and took apart all had absolutely wrecked o-rings and zero cylinder head air sealing.
But these were all obviously standard ootb blasters that were of really impressive quality and value at the time, and were very suitable for being upgraded/improved from their standard parts……… all of those issues were nothing more than poor QC on a mass produced product.
A simple build plan for the base upgrade for any of my customers was nothing more than stripping down the stock CYMA/JUND, fix the air seals, replace piston o-ring, fit a ChiHai High Torque Red Motor, shim, metal 18:1 gears, AUSGEL 1.18 spring, tighten tappet spring, 11.1V battery and upgraded wiring/plugs.
Easy 300+ FPS with 18-20 RPS, smooth, reliable, efficient and a solid base for the customer to add whatever hop-up and accessories that they wanted to add to them 
Certainly can’t knock them for a great quality first blaster for anyone looking to get into the hobby…… but I’ll still stick with my old Gen8 M4’s, HK416’s, UMP’s and ACR’s thanks! 
I’ve had plenty of CYMA M4 CQBs that I’ve used as build platforms. They’re a bit of a weird mix of quality and shite, which is what you’d expect at that price point, I guess. 
I had about five, now I’m down to one, and the only thing original on it is the receiver shell. 
Standard mods for all of mine were 7.3 inner barrel, o ring and M90 spring… oh and a replacement for the ultra thin handguard. I happen to like vertical foregrips and the stock CYMA nylon item flexed just enough to trigger my OCD, so an alloy handguard was pretty much mandatory. I didn’t have any issues getting them up around 280FPS and the accuracy was acceptable with the tighter bore IB.
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Didn’t I have a cylinder head and nozzle in there already?
I know it had a good seal when I ran it😅
Found the chronograph results with UE’s
Just search M14 EBR in this thread and you will see even with glowies it was even more consistent
After a similar lot of mucking around with CYMA/JUND sort of settled on:
- 100% cylinder
- aftermarket metal double o-ringed cylinder head and nozzle (to suit CYMA) - with appropriate dab of silicon grease
- SHS M100 spring
- metal or standard gears 1:18 (still can’t find a metal non-return that suits CYMA)
- suitable piston and lubed o-ring with AOE set on any metal rack / metal gear combo (stock blue gears seam to run OK)
- 7.5mm barrel with length in v/e ratio of 1.65 to 1.75
- red motor
- metal hand guard, usually Noveske)
- Uband hop-up (although one still had ihobby SLR hop-up/flash hider)
Getting between 325FPS and 350 FPS with that combination, dropping to closer to 290FPS with AUSGEL spring
Going to take the guts out of the always inconsistent ACR/R and build another CYMA box and stick with CYMA M4s and AUG Gen 8’s and eliminate unnecessary variations
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You did, Mutha… a upgrade brass double o-ring nozzle and cylinder head. Oh and the piston head was cracked, but there’s a new alloy item in there now. Awesome compression in the assembly out of the blaster so I know I’m good there.
The issue I’m having with low FPS is definitely air seal at the t-piece and probably nozzle length related. I know the Gen 8 nozzles are slightly shorter than the BF item, so I tried spacing a Gen 8 nozzle out with first one, then two, then three o rings.
Best results seemed to be with two, three o rings caused feeding issues. Still, highest figure I’ve seen on the chrono is around 200FPS.
Ah, it’s all good, Mutha… I wanted a project, if I’d put this sucker together and hit 300+ without having to fettle, I’d have been disappointed. 
and I’m having a lot of fun with it, like a blast from the past.
The next step is trying a Vector or AUG nozzle in it, they’re slightly longer than Gen 8.
POST EDIT : 98FPS with the Vector nozzle in.
On the upside I did manage to fit a top pic rail so it can run a fake LPVO.
Spacing out the nozzle rubber is a fine line between extra sealing pressure and leaving enough space when retracted to feed gels past the nozzle…… but on some blasters where the rubber spacing caused feeding problems, it was sometimes possible to add an o-ring to the actual t-piece face itself to compensate.
This depends upon the design of the t-piece though, some have a good depth forward of the gel feed tube to add to, whereas others have the feed tube actually cut into the nozzle sealing face itself
This can be another thing to check if losing air pressure, the t-piece face where the feed tube intersects the barrel/nozzle face.
Some blasters which have the feed tube at 90° very close to the barrel end have the feed tube cut deep into the nozzle seal area, allowing much of the FPS to escape down into the magazine
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You can order heaps of stuff from here, but just need to contact them and send via normal post and remove any references to Airsoft from the shipping paperwork/packaging
What kind of adhesive would you use for glueing a nozzle and/or one of those cylinder head pads ( one that goes on the inside face of the cylinder, think it’s called a buffer pad)?
I’ve heard Loctite, the blue or the black one if your really certain. I don’t know what works well for sticking rubber to metal.
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Gorilla glue. From one of the old forum members, works well.