Jinming j9 upgradability recommendations?

title says it all. i have my j9 m4a1 laying around and its basially stock with the exception of the rail handguard. im thinking of upgrading it but im not too sure on what to upgrade on.
so far ive brought a m90 spring of aliexpress and im thinking of getting a 30mm aluminum barrel but im not too sure of the other upgraded as im a noob to this kind of stuff.
the main component is the mosfet, i want my gun to feel more snappy and responsive and ive heard that a mosfet can help but im not sure which on is a good one or will fit in my gearbox. so far ive found this: 12.23AU $ 50% OFF|Airsoft Age|airsoft Gel Blaster Mosfet Module With Active Braking & Overheat Protection
but im unsure if it’ll fit so maybe you could recommend a mosfet?. another thing is ive seen that i’ll probably need to solder but i have no experience doing or the equipment to do so.
im also thinking of a battery upgrade to 11v but not sure if its safe on a stock blaster. another thing is shimming, ive seen some videos on it but im still unsure on what ratio and if i need any other equipment of can i just use the stock gears and not worry about buying anything else?

the mosfet i found says external mosfet but im unsure wether that means sits outside the gearbox or will it fit in

Think it was like an easyfet, sitting in the buffer tube sorts thing

Yeah, there’s definitely no room in a Gen 9 receiver for a MOSFET. Too tight. The major benefit of a MOSFET is fire control and trigger response, but adding one into the equation can introduce another point of failure further down the track.

The Gen 9s were a bit odd in that they were almost V2 but had a slightly different shape to the shell, curved at the back of the box and not straight like most V2s. MK brought out a CNC gearbox for them called the Hybrid.

Personally I wouldn’t throw too much money at a Gen 9… there are plenty of better M4 platforms around now which would give you a much better result. But if you really want to upgrade yours I’d recommend an M90 or 1.2 unequal spring, an upgraded o ring cylinder head and nozzle, and maybe an alloy piston head. Get the airseal right and you should acheive 280-290FPS easily enough. Your stock nylon gears should handle the upgrades if you don’t go overboard with your spring.

If you want a snappier trigger you could always look at upgrading the motor to a high torque / high speed item. This does put more strain on your gears though, especially the motor pinion gear and bevel gear, so swapping over to metal internals is usually a good idea if you make that upgrade.

There are tons of snappy blasters out there that don’t run MOSFETs, they get their performance through a great setup, gearing and motor choice.

yeah im thinking of getting a better blaster once ive moved out. regarding the motors, do i want a L or S motor and should i try a brushless motor or no? ive already ordered a m90 spring which will arrive around march from aliexpress. i might get an aluminum barrel but im not too sure of the head and nozzel as stock nozzel should be fine?

You need a 460 long shaft motor for a Gen 9.

These go well in a Gen 9…

You can run the stock nozzle, etc if you prefer. You’ll gain FPS if you upgrade.

At a minimum, if it were my project I would run an M90 spring, upgraded nozzle, cylinder head and piston head, upgraded o ring, alloy inner barrel, stock motor, 11.1v battery. That’s pretty much a basic upgrade and should punch around 280.

i kinda want to make my trigger more responsive and snappy, want to go semi more than full auto

some other questions:

  1. ive seen people say get a better o-ring (green) but does size matter? can i get any green o-ring or should i try find onces made for aegs?
  2. do i need to upgrade the cylinder or can i leave it be?
  3. what aluminum barrel length should i get, is 300mm fine or should i try get a 350mm
  4. is there a way to change the handguard to a bigger or CQB length? can i remove the metal bit which is meant to serve as the gas block?
  5. if i get a 11v battery for faster ROF, what should i upgrade to make my blaster more compatable and not break faster
    might ask more questions later but this is all i can think rn

The O-rings should be a standard size, can’t think of it rn, but then one are a better material compared to the black ones and seal better.

If the cylinder isn’t damaged then there’s no result any need to “upgrade” it, really as long as it’s smooth inside there’s no issue, some materials have a smoother finish but if the piston head is lubed it won’t really make a difference.

Barrel length really only depends on how long you want the blaster, also whatever matches the cylinder for volumetric efficiency, there was a thread somewhere about it that had an in depth look at it, you can change to a ported cylinder if you want a shorter barrel and the reverse for a longer.

The J9 uses a standard thread for barrel nuts so really any handguard with a barrel nut will work, I got a random metal 9" one on my J9 and it fits just fine, I did use a barrel stabiliser inside the handguard just to hold the barrel centre thou being a bit longer, also makes it a bit sturdier.
The gas block is just cosmetic, worst case you can just replace the entire outer barrel with whatever you need.

For the battery, a better motor, and as FriendlyFire said, you should upgrade the gear train in kind.
Running a higher ROF creates a new problem with piston timing where the gears can cycle faster than the piston can be reset, if you don’t have a higher spring in there, and it locks the piston back, like the release tooth of the piston gets caught by the pickup of the sector gear and it can’t be posted back resulting in it being locked to the rear. You can get around this by short stroking both piston and sector gears thou.
That’s why I’ve gone back to using 7.4v but higher spring and stronger motors, CBF grinding teeth.


7.4v lipos give a more realistic ROF anyway IMHO… unless you’re a speedy boy chasing stratospheric numbers :rofl:

If you compare green o rings to the factory o rings they’re usually a little thinner and slightly larger. All goes to better sealing against the cylinder wall.

They’re meant to be loose on the piston head, so first time changing one you’ll probably think it’s too big.

Go have a look at this… one of Low Guido’s older videos on Youtube and specific to a JM Gen 9. It’ll help you get the basics of upgrading any blaster down. :+1:

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My opinion on gen9 is they are best left at the value and easy performance level which is also reliable…

335mm alloy barrel.
M90 spring.
Green oring
Stronger Return spring
Brass cylinder head and nozzle.
Spring retainer

Run that on 11v

You will have a blaster that will last ages through all sorts of abuse. Cheap reliable performance.

Anything higher rof and fps needs metal gears, and the effort involved combined with the gearbox flexing it induces ruins the reliability too much imo making it not worth it. If you want to go further than that get the mk h92 gearbox and do whatever your wallet and skills desire.

should i (or can i) use a brushless motor? also what are the benefits and is it easy to setup?

Apart from costing more than the blaster is worth, it’s probably not worth it. Brushless is like the final upgrade before going to HPA, kinda.
Just going off what I’ve heard/read they tend to be finicky when used with FCUs (unless stated otherwise). They’re not really hard to set up cause they have a control board on them already but I’ve heard of issues with batteries not working properly, something with the C rating not being good enough or something.

You’re better off just using a decent normal motor for something like a J9.

Given the gearbox flexes with a stronger motor and spring I would definitely not recommend a brushless motor as they have more torque than a brushed motor.

As @Friendly_Fire commented previously, the ChiHai 460 Red long motor is more than enough grunt/speed for pretty much everything except the much higher end modified blasters, especially with anything running older Nylon Gearboxes!

I used them exclusively in all of my extreme FPS experimental Nylon blasters/customer builds, as well as in my own personal collection as a very well priced but powerful motor.

Accompany this with a quality high output battery, upgraded trigger switch and upgraded internal wiring size ……… the result is a very snappy trigger and great ROF that’s not too high as to cause feeding issues in other parts of the system :ok_hand:

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I can tell you from experience that the nylon gearbox shells in Gen 9s ain’t the most robust out there… I know a few people who swapped them out for MK Hybrids because in their quest for stupid high ROF and FPS the stock nylon box crapped out at the bearings. From memory, they’re not the easiest boxes to shim gears in either. Not impossible but not Gen 8 easy.

As @DocBob says, keep to his recommended parameters and you’ll have a solid setup that’ll last. :+1: just don’t go nuts with it.

I wouldn’t throw a brushless into a Gen 9… that’d be in the category of going nuts with it. As @DChapo rightly says, it’d be worth more than your blaster.

I know you’ve already got the Gen 9 and that’s why you’re looking at upgrading it… and that’s understandable. Someone I know was looking at a Gen 9 recently, I steered them to this one.

Everything’s already upgraded, nothing to do and it’s from Double Bell, a company that still exists. Unlike Jin Ming who are now defunct :wink:

Pretty hard to beat anything made by Double Bell as a true well built/good performance blasters out of the box :ok_hand:

I certainly found the weird Gen9/Gen10 boxes to be less rigid than the good old faithful Singularity Gen8’s for sure!

I still have an MK Hybrid Alloy box stashed away somewhere, as it was definitely an expensive/rare part that I couldn’t bring myself to throw in the bin with the majority of other parts at the time.

The Singularity Gen8’s were my bread and butter, whereas after trialling a few Gen9/10 builds, I quickly steered away from them.

Certainly not difficult to get a good sweet spot of 300 fps from a Nylon Gen9/10, but it certainly takes a bit of knowledge and experience to get all the correct components/mods right to make them work reliably and consistently :ok_hand: