need experts' hand

[nexus]

I bought an AK-74 Toystar from gunday.co.kr
The first test shooting was so weak that bbs fall within few meters maybe around 100fps and I opened up the AEG and installed missing hop up unit.
But it is still not at 300fps after all and it penetrates coke can shooting more than twice at the same spot. I guess it is shooting around 200fps.

So I opened the gearbox which is cm.02 (cyma gearbox version 3) I guess even the gun itself may be AKs-74 by CYMA (CM031C) not Toystar.
Then I checked the cylinder air seal by blowing into it. It was perfect no airleak. But when I blow into the cylinder nozzle while the piston head is still in the cylinder with half compressed position there were some air leak. :confused:
Is that normal for piston to lose air by its O-ring rubber when blown from the nozzle?

Should I upgrade its spring and battery for better fps and rate of fire?
what type of spring is preferable? and also for the battery?

for the battery I found this info. don't know it is true or not

you're going to have to time your charges to avoid overcharging.

It's rather simple to figure out how long to go for...

you need to know three things, the capacity of the battery (the mAh number written on it), the output of the charger in mA (should be written on the charger) and the type of battery (ie NiMh or NiCad)

The formula is simple:

(capacity / charger output) x 1.4 (for NiCad)

or

(capacity / charger output) x 1.5 (for NiMh)

The resulting number is the number of hours you need to charge for. Bear in mind that the answer is a decimal, so 9.5 is nine and a half hours and not nine hours and fifty mins. (Obvious I know, but this confuses some people).

For example:
I have an 1100mAh NiMh battery and a charger with an output of 180mA.

this gives;

(1100/180)x1.5 = 9.16666

9.166666 hours is 9 and one sixth hours or 9 hours and 10 minutes.

[krobinson103]

Don't waste your time. Get a better one. You'll spend days fixing it and you will be always expecting it to work...

[Righteous]

The piston head should have an o-ring around it that makes contact with the inside of the cylinder. If it is not a tight seal then the piston will leak air. It should not leak any air.

[nexus]

Thx for replies :)

For the fps problem

...I'd also check the spring, like buy a M100 and see what you get out of it...other than that you gotta check the hop up unit is functioning correctly, and if you haven't upgrade the bucking to a better brand like prometheus...


I'll try using this spring and if it doesn't work I'll look for piston or airseal nozzle.

[krobinson103]

I've run into a problem where the piston itself was a fraction too small for the cylinder . This caused the bb to roll out the end. I tried changing the piston head and o ring and this solved the problem. Assuming there are no compression problems you can just put a more powerful spring in.

Be aware that this will slow the ROF and wear the parts more quickly. Its better to stay at about 100-120 on spring ratings and get more power from better sealing parts.

Its possible to increase your fps with bearings or spacers on the spring guide and piston. Be careful with this. If you get too much spacing the gun may not fire at all. I know... it happened to my gun. The piston couldn't retract far enough to disengage and thus jammed with a fully compressed spring... every time.

If there is no problem at the gearbox end it is due to the hopup unit. As suggested earlier try changing the hopup bucking to a really good one. It will make a difference. There is also a chance you are losing pressure in the hopup itself. You can get tape to seal the unit and ensure there are no leaks.

You may also want to simply clean the barrel. Its amazing how much gunk there is in the barrel of a new AEG and it really slows the bbs down. If it is clean then you can upgrade the barrel to a 6.04 or less and you will see an increase of 20-40fps.

It all gave me headaches thus my orginal post... get a gun that works the way it supposed to in the first place. A year of fighting to get my gun working ended in it being scrapped for parts to service my new gun. easier all around.

[nexus]

Well, I finally figured it out :).
The Problem wasn't the spring or piston but the tiny little plastic semi ring set on the nozzle preventing it from pushing the bbs into the hop up chamber completely. I just removed that thing. Now my gun shoots over 300fps cause penetrating the coke can on both side and almost putting a hole on the bottom of the can LoL :cool:.

I guess I can control the fps by cutting the length of the semi plastic ring for 300fps thus I need speedmeter or some sort of tool measuring fps for adjustment in our next game.
I would be really appreciate if one has it :D

[krobinson103]

You are shooting close to 400 if its almost going through the bottom. That gun is out for playing against any Korean team. You have 2 options.

1) Put the old spring back (or even better a m90)
2) Use a reducer. This will reduce it, but the Koreans don't like them much

I suggest number 1 as the best option.

[nexus]

You are shooting close to 400 if its almost going through the bottom. That gun is out for playing against any Korean team. You have 2 options.

1) Put the old spring back (or even better a m90)


I didn't change the spring it is stock spring. But I already ordered M110 which is little longer than my stock spring and got M110 yesterday.
I might need lower spring or just put the semi plastic ring cutting its length in half or some sort.