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Ak Shoots Too Hot


Asylum_88

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Okay, so I've scoured the forums and haven't found a topic on this issue.

I have a buddy who has a CYMA AK (not exactly sure which specific model), and it shoots over 400 fps. I've seen fps limits on many fields for AEG's be 400 fps with .20's, so my question is.. anyone have any advice to lowering fps? Will I need any new parts? Etc.

 

From what I've seen and read, the Chill and Grill is coming up and some tech things happen there. I unfortunately may not make it due to work (unless anyone is still there past 5 pm), and my buddy isn't too tech inclined.. so he may not make it either.

 

Any tips, tricks, and hints would be greatly appreciated!

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I've seen some people recommend leaving the spring compressed for a day or so.

 

More than that. Typically, to get a drop of 15 FPS, you need to have it compressed a week or longer. I recommend that the user cycle it daily, leaving it compressed over night each night. 

 

Most springs, even after compression treatment, will not drop any more than 15-20 FPS, most of the time--less. 

 

The most effective solution is always to just get a new spring. $10 and time on YouTube will fix the problem in a jiffy. 

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I second Rogue's suggestion on the spring swap.

 

Target Practice ran into this very same issue recently.  His AK had a M110 spring in it, but it was firing a little too hot for his liking.  Swapped out to a M100 and all was well.  Didn't care much for all the trouble closing that Echo 1 Ver. 3 gearbox though.. :D

Edited by Endgame
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Hmm spring compression, makes sense. I'm still relatively new to the tech side of airsoft so forgive this next question. To keep it compressed, will it need to be taken out of the gearbox and kept in a vise, or something along those lines? Or is it possible to cycle the weapon and leave it in between a full cycle of the trigger pull?

 

We'll certainly try the compression method first, but if a spring swap is what it needs we'll go from there.

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OK, you know when you pull the trigger, you hear the motor wind up and then it releases and you hear the pop?  The trick is to pull the trigger and let go so fast that the piston is pulled back but not released.  Which Cyma AK do you have, by the way?  I know they made one that's way too hot, like 420fps or something insane like that.

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To keep it compressed, will it need to be taken out of the gearbox and kept in a vise, or something along those lines?

Only one way to find out. :P

Edited by Comrade Wichita
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To keep it compressed, will it need to be taken out of the gearbox and kept in a vise, or something along those lines?

 

Only one way to find out :P You certainly could do that, but at that point you might as well just put in a new spring

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OK, you know when you pull the trigger, you hear the motor wind up and then it releases and you hear the pop?  The trick is to pull the trigger and let go so fast that the piston is pulled back but not released.  Which Cyma AK do you have, by the way?  I know they made one that's way too hot, like 420fps or something insane like that.

I know exactly what you're telling me, I'll tell him to do that.

This is the model that my buddy has, it isn't mine. But you're right, I think when he got it the little paper said it was shooting between 410-420 fps..

http://www.airsoftgi.com/product_info.php?products_id=3888

 

 

Noxtoof and Comrade Wichita: haha I had realized that after I posted :facepalm: but I'll see what he decides to want to do and go from there.

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Unfortunately your best bet is to replace the spring like the other fellas have said, since it's really hard to predict how much tension you managed to take off the spring by compressing it. 

Edited by targetpractice
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Understood. Thanks guys, I really appreciate the help! That should give me a decent starting point for my buddy and I. We plan on going March 1st to the VBR open play game, so hopefully it's done by then.

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I'd recommend a new lower-powered spring, do it right the first time.

 

I've seen a lot of "compress your spring for a week" nonsense over the years, I'm not sold on it. Springs physically wear out over time from use, not from being compressed. Any compression spring that can lose power from being compressed for a week, even coil to coil, isn't properly heat-treated in the first place. JMHO.

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If you haven't opened up a gearbox before, I'd recommend you take it down to Chill and Grill, which is the week before.

I'd like to go to the Chill and Grill, but I work on that day.. unless anyone is there past 5 pm then I may consider going. The only gearbox I've open up before is my own AGM M4 (it's a long Franken-build story).

 

I probably may recommend telling him to get a new, lower powered spring, but until he has some spending money we're going to try the spring compression idea. Keeping all viable options open!

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You can put a limiter in it or slap a lower compression spring inside. My team uses a CYMA ak74 that shoots 460fps. We use a limiter on the motor and use a cheaper spring inside

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Have you actually chrono'd it? Websites fps are usually set higher than what that actually are.

CYMA AKs are over 400 FPS stock.

You can put a limiter in it or slap a lower compression spring inside. My team uses a CYMA ak74 that shoots 460fps. We use a limiter on the motor and use a cheaper spring inside

 What?

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 What?

 

Seconding that what. How on earth would a limiter on a motor affect the FPS of a gun? To me, it seems like it would only limit rate of fire. And what exactly is meant by "limiter?"

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You can put a limiter in it or slap a lower compression spring inside. My team uses a CYMA ak74 that shoots 460fps. We use a limiter on the motor and use a cheaper spring inside

 To be clear, the rotational speed of the motor has nothing to do with velocity. 

 

The only way the motor can affect velocity is if one of two very bad things happens:

1. The piston is pulled back too fast for the air to fill the cylinder -or-

2. The gears spin too fast and short-stroke the piston cycle

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You can put a limiter in it or slap a lower compression spring inside. My team uses a CYMA ak74 that shoots 460fps. We use a limiter on the motor and use a cheaper spring inside

1352080856675_zpsc7bcee2b.jpg

 

 

I assume, or at least certainly hope, you mean a lower rated spring, not cheaper. Price shouldn't have anything to do with how hard it shoots. I won't even address the limiter. Rouge explained that pretty well already.

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I'm glad you guys decided to answer on that "limiter" comment, I was lost..

 

But thank you all for the help, tips, tricks and so on! I'll tell my buddy to have the spring compressed for now, chrono'd and then if need be, change out the spring to bring it down under 400 fps.

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Depending on how old the gun is, if he goes ahead and breaks into the gearbox, tell him to put in a new O-ring as well to keep compression good. Kimball Midwest #14 are the best in my books. Tell him to go ahead and check the shimming as well if he feels up to it. Those will help with all around performance.

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