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Cyma AK shooting 365 fps

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Hi all.


I need to downgrade the spring for just under 350 fps.

What spring should I buy?


Thanks for any help.

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You need to provide more info.


Do you know what it currently has?  Is it stock?  Was it new from somwhere abroad, if so the website might tell you what spring it has.


If not we'd just be guessing, but if I had to guess I'd say you probably need an M100.  But if you have a highly optimised AK, it might already have an M100 in there, in which case M90 or M95.


You could also short stroke it.




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Easiest option - correct AoE

(the cylinder head will fall out no doubt) 

That should drop 10 to 15 fps


Just that one thing should do it


You could, remove the heavy 8mm alloy spacer inside the piston

you need a m3 nylon nut & penny washer

This will lose about 40fps I'd say as it will not compress the spring as much now

(it is about same as short stroking 3 teeth off - but you don't lose volume)


If it is a full size AK with a 455mm barrel you can't Short Stroke as you need max volume

Could SS a 74 with a 250~275mm barrel but need new piston with more metal teeth on rack

SS 1 tooth for a 400mm barrel

SS 2 teeth for a 350mm barrel

SS 3 teeth for a 300mm barrel

you can take an extra tooth off at a push but those are examples I tend to go with on volume 



Don't worry too much if some most of this way over your head - just saying


If you drop spacer, then you need to improve seals, the o-ring is so-so on piston head

wrap ptfe around the cylinder head to seal better

could maybe change nozzle if you wish but there are two AK nozzle lengths


To be honest, the least amount of f*cking about - correct AoE

leave most of it alone perhaps and should be near 350fps


If you start improving seals you likely will hit 400fps

then you need to remove alloy spacer as well as AoE


I mean you should if you was going to do it correctly

gets seals really good, drop the alloy spacer, AoE, regrease etc...

Then pretty sure you should have a 350fps gun cycling more efficiently

and not needing to compress the spring quite as much

all for next to nothing


Or buy say a m95/m100 spring

but problem is some springs can come in a bit higher/lower than expected


generally you want a m95/100 for a full AK 455mm barrel

or maybe a sp85/90 if it is a Garder spring

(don't ask me about springs with percentages - fuctifino is the answer there)


Personally I'd work with what you got if you know it is 365fps and go from there

plus it is cheaper - no ordering of bits if you got asay a 22mm x 3mm rubber washer to correct AoE


Or get more involved with sorbo/silicone, ptfe, m3 nylon nut, new/stretch o-ring etc...

Still cheapy options working with what you got already but that is just my take on stuff

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Er, lop a coil or two off the spring?  No need to over-complicate things.

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Lopping coils is a bit of guess work

plus need to finish/straighten coil end


a 20~22mm x 3mm thick washer (not perfect like sorbo/silicone)

that will reduce stroke by 3mm aprox = about 13fps like short stroking 1 tooth

Correcting AoE & dropping 13fps - a washer & some superglue


clean up cylinder head (washing up liquid to degrease)

check old existing washer on stock head, if in doubt remove and clean up

bit of cheapy poundland superglue...

Plop plop

refit old & new washer adding 3mm to correct AoE

(or two washers if old washer ripped apart on removal)


slap it back together - couple of minutes no hacksaw/pliers/molegrips/vice/file required


Personally I'd be tempted to redo seals drop spacer but I'm a tart I guess

but reckon cheapy simple no frills or extra messing with other stuff just correct AoE

should do it about right - quick, easy & very cheap without too much work or guessing stuff


Obviously if get seals really great then gun will likely shoot 390fps and have to remove spacer

nah pull it apart carefully just correct AoE - ya gun's std piston will thank you for it in the long run

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21 hours ago, Sitting Duck said:

Lopping coils is a bit of guess work


I'd guess 2 coils.  I'm pretty awesome, I just chopped my sniper down from an insane-in-the-membrane 600 to spot on 495 with one mighty cleave. ;)



21 hours ago, Sitting Duck said:

plus need to finish/straighten coil end


10 seconds on a gas hob.

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2 hours ago, Huxley said:


I tried that once, it didn't go well......

Did you buy it dinner first ? If not there’s your problem ! 😉

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Thank you for the advice :D


I will do the correct AOE first and see.

And I need to buy myself a chronograph at some point.


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