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Reducing FPS problems


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#1 Kilgannon

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Posted 01 December 2008 - 08:34 AM

i have the KWA M4 tactical which was chrono'd at 410 fps with everything stock.
i have switched out the spring guide and spring for an area 1000 non-bearing spring guide and a jbu m100 spring. i also put in a 407mm tightbore barrel(i was told this should only up the fps by 5-15). with all this i am running the RA-Tech 11.1v lipo in it.

now the problem i have is that even with what i thought would big downgrades it is still chronoing at about 390-410 fps. this seems wrong. my friend has the m4 tactical also and has done all the same changes except the tightbore barrel and his is still shooting with a high fps also(around 390). is there something in the KWA's that are making them shoot hard that i don't know about? could it be the lipo?

any help would be appreciated. i'm trying to get it in the 350-360 fps range.

#2 Stealthmaster14

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Posted 01 December 2008 - 08:58 AM

You put in an M100 and you are getting over 400 fps!!?  Either you mean an M110, or JBU springs run really hot. (I doubt your compression is that good if it is stock....ha ha)  If it is an M110, you will need to let it settle in. Afterward, the fps should drop from about 20-30 fps.

Edited by Stealthmaster14, 01 December 2008 - 09:00 AM.


#3 Kilgannon

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Posted 01 December 2008 - 10:10 AM

i bought the JBU at my local shop and they told me the JBU's are pretty weak. the package says m100 on it. when i put it in i could tell it's not a real stiff spring like the stock one, but maybe it got packaged wrong at the factory and it is an m110? i've heard that this happens sometimes.

the really strange thing is that my friend's is doing the same thing. i don't know what parts he used to downgrade, but it's like KWA's are on steroids.

i'm tempted to go to an even lower spring, but then i'm afraid the piston won't make a full push before the gears grab it again.

#4 Lt. Tony

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Posted 01 December 2008 - 10:49 AM

What kind of FPS are you looking for?

#5 vic_man4

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Posted 01 December 2008 - 06:54 PM

View PostLt. Tony, on Dec 1 2008, 11:49 AM, said:

What kind of FPS are you looking for?

View PostKilgannon, on Dec 1 2008, 09:34 AM, said:

i have the KWA M4 tactical which was chrono'd at 410 fps with everything stock.
i have switched out the spring guide and spring for an area 1000 non-bearing spring guide and a jbu m100 spring. i also put in a 407mm tightbore barrel(i was told this should only up the fps by 5-15). with all this i am running the RA-Tech 11.1v lipo in it.

now the problem i have is that even with what i thought would big downgrades it is still chronoing at about 390-410 fps. this seems wrong. my friend has the m4 tactical also and has done all the same changes except the tightbore barrel and his is still shooting with a high fps also(around 390). is there something in the KWA's that are making them shoot hard that i don't know about? could it be the lipo?

any help would be appreciated. i'm trying to get it in the 350-360 fps range.

My suggestion is to let your spring settle in a bit and see if it comes into that FPS range, other than that you could just downgrade the spring again till you get it right.

#6 brooklyn468

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Posted 01 December 2008 - 07:16 PM

View Postvic_man4, on Dec 1 2008, 08:54 PM, said:

My suggestion is to let your spring settle in a bit and see if it comes into that FPS range, other than that you could just downgrade the spring again till you get it right.

Yes, try that.

#7 Guest_allizard_*

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Posted 03 December 2008 - 12:49 AM

For the record,

11.1 lipo don't increase FPS.
6.03mm TBB may increase between 10-15fps.
6.01mm TBB may increase between 15-30fps.  This is from a 6.01mm EDGI M4 barrel I have tested.
m110 spring CAN push 400 fps when the air seal is very good.

#8 jvelten

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Posted 15 December 2008 - 10:13 AM

I am having the same problem with my M4A1 CQB. Stock it is shooting 392 FPS, which is much too hot for any skirmish down here in Florida. I purchased and my team tech put in a JBU M100 spring and it shoots even hotter. So for now he cut down the stock spring and that helped by reducing the FPS to around 310. I plan on ordering a couple of other springs like a PDI 140% and System M100 since I've heard that those are fairly consistant. It just frustrates me that I purchased this CQB because it was suppose to be 350 FPS or slightly lower, but it appears that during construction an M120 was installed instead of their M110. I can't explain why the M100 is shooting so strong either. I'm not getting any where with the techs on this site so I had no choice but to refer to our team techs. Once I get the new springs I'll try both to see which one will get me closer to the 350 FPS golden number... I'll keep you posted.

#9 Guest_allizard_*

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Posted 15 December 2008 - 10:25 AM

firstly, the spring need time to settle.  And the chrono may need re-calibration.  It's very odd that a JBU m100 shoots even hotter.

#10 jvelten

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Posted 15 December 2008 - 10:58 AM

View Postallizard, on Dec 15 2008, 01:25 PM, said:

firstly, the spring need time to settle.  And the chrono may need re-calibration.  It's very odd that a JBU m100 shoots even hotter.

I know and we can't explain it. I placed the order for the System M100 and a PDI 130% today and I should have them by the end of the week. Unless the compression is unbelievable I'm hoping that one of these will fix the problem. I know that springs need time to settle in but it was shooting 392 stock. I still need to put in my tight bore barrel which will increase the FPS. I'm guessing that if let alone it would bring the FPS well over 400. I need this to shoot 350 by January 10 for a tournament.

#11 jvelten

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Posted 15 December 2008 - 11:08 AM

Just want to make a point here. I'm not bad mouthing KWAs, I feel that mine is the best airsoft weapon I've ever owned. I'm just trying to resolve my FPS issue so I can use it against other players instead of just paper targets...

#12 karMeister

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Posted 15 December 2008 - 11:47 AM

HAHAHA! now we have people complaining about an AEG being too good  :lol:


Seriously I see the point about FPS limits. JBU springs are not that popular here so I cant comment about them. PDI however have alot of inconsistency issues (wrong spring on package/fake springs). I would  say a systema M100 would do the trick or a stock low end AEG spring(Dboys,Jinggong...Echo1 etch)  or stock Marui spring...

#13 jvelten

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Posted 16 December 2008 - 04:05 PM

View PostkarMeister, on Dec 15 2008, 02:47 PM, said:

HAHAHA! now we have people complaining about an AEG being too good  :lol:


Seriously I see the point about FPS limits. JBU springs are not that popular here so I cant comment about them. PDI however have alot of inconsistency issues (wrong spring on package/fake springs). I would  say a systema M100 would do the trick or a stock low end AEG spring(Dboys,Jinggong...Echo1 etch)  or stock Marui spring...

No, I'm not complaining about the gun being too good, just too hot for competitions. I purchased the KWA M4A1 CQB because it was suppose to be at or just under 350 FPS. This CQB was tested at airsoftgi at 384 and consistantly with my team at 392. It would have been tagged as a hot gun and not usable. Anyway, for now we trimmed the stock spring down and it's shooting 310 with .20 bbs. Once I get the Sysetma M100 I'll see how that does.

#14 Lt. Tony

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Posted 16 December 2008 - 06:12 PM

View Postjvelten, on Dec 16 2008, 07:05 PM, said:

No, I'm not complaining about the gun being too good, just too hot for competitions. I purchased the KWA M4A1 CQB because it was suppose to be at or just under 350 FPS. This CQB was tested at airsoftgi at 384 and consistantly with my team at 392. It would have been tagged as a hot gun and not usable. Anyway, for now we trimmed the stock spring down and it's shooting 310 with .20 bbs. Once I get the Sysetma M100 I'll see how that does.

First KWA uses the same spring in their M4A1, gearbox, and the CQB version the only difference is the cylinder. I would swap that out, that will up your ROF, and decrease your FPS. Also put about 2-3k rounds through your gun this should help the spring settle. and don't use a systema spring, use only promy, or PDI, and change out your cylinder, and you should be good. Also makes sure that your gun has the hop-up adjusted properly. If your hop-up is all the way off then your gun will chrono much higher, if it's all the way on then much lower.

#15 eXiLe.

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Posted 19 December 2008 - 04:10 AM

honestly the kwa gearbox is amazing no matter what spring yo get it will come out with ahigher fps and the reason i think this is because of the bearing on the spring guide the covers are underneth it and ontop of it so it puts more tension on the spring this is why i belive your getting a higher reading on the jbu m100 i put a jbu m90 stock spring in mine and i get 350 wich i am suposed to be getting 320 max but with good seals and the bearings on the spring guide its easy to jump up 30fps. This is just what i have seen but may not be accurate.




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