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Lowering FPS?


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#1 Prototype

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Posted 06 September 2010 - 05:17 AM

I was thinking about getting the Kmp9 for cqb, however my field has a 350 fps limit. I think this gun would be perfect, but when I watch video review I see this is shooting at like 440 FPS. Is there anyway you could lower the FPS on this? My field has the option for .25s would that lower the FPS enough?

#2 cjboi

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Posted 06 September 2010 - 05:11 PM

get an RA TECH npas kit, although most people here wouldn't recommend the NPAS kit since it would void your warranty and you might possibly break your own gun.

#3 Gun487

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Posted 06 September 2010 - 06:21 PM

You should have .25's anyway. If that is not enough then use duster gas.

#4 gcw360

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Posted 06 September 2010 - 07:12 PM

View PostPrototype, on 06 September 2010 - 05:17 AM, said:

I was thinking about getting the Kmp9 for cqb, however my field has a 350 fps limit. I think this gun would be perfect, but when I watch video review I see this is shooting at like 440 FPS. Is there anyway you could lower the FPS on this? My field has the option for .25s would that lower the FPS enough?
You need to clarify what options you have with .25's at your field.  Typically you will chrono with .2's and then have the option to play with .25's.  Using .25's to lower the FPS is not cool.  The same amount of energy is delivered regardless of the drop in FPS and it is considered cheating the chrono to use .25's to drop the FPS in order to qualify. :gun:

#5 Vamp2269

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Posted 06 September 2010 - 07:37 PM

I guess it's doctor who week around here. LOL

You could try to find a rocket valve that lowers the fps, but then your still voiding the warranty. If you wait the 45 days then go ahead and do it, if you break something KWA will fix it...for a price.

And lowering fps with different weights is bad, it doesn't lower the joules the bb delivers on impact. I always have to explaine this to my friends.   :thumbsdown:

Edited by Vamp2269, 06 September 2010 - 07:39 PM.


#6 cjboi

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Posted 06 September 2010 - 07:56 PM

duster gas!!!

#7 Prototype

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Posted 06 September 2010 - 09:16 PM

View Postgcw360, on 06 September 2010 - 07:12 PM, said:

You need to clarify what options you have with .25's at your field.  Typically you will chrono with .2's and then have the option to play with .25's.  Using .25's to lower the FPS is not cool.  The same amount of energy is delivered regardless of the drop in FPS and it is considered cheating the chrono to use .25's to drop the FPS in order to qualify. :gun:

You're right, I just read the site rules and they chrono the rifle with .2's. I wasn't trying to cheat the chrono, I just didn't realize the same amount of energy is delivered by doing that lol.

So really the only way to lower the FPS is by using a NPAS Kit? I'm really new to GBB, is doing that easy?

#8 Spiggy

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Posted 07 September 2010 - 11:01 AM

Duster gas is the cheap alternative.  Considering you can find a case of canisters for near $4 per can.  You can use a MP7 nylon jet nozzle, it will drop it around 360 or so with green gas.

#9 xKingSizex

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Posted 10 September 2010 - 04:46 PM

View PostSpiggy, on 07 September 2010 - 11:01 AM, said:

Duster gas is the cheap alternative.  Considering you can find a case of canisters for near $4 per can.  You can use a MP7 nylon jet nozzle, it will drop it around 360 or so with green gas.

Allizard and I tried using duster gas while in the testing phase...it's not strong enough to cycle the bolt on full auto. It was okay on semi auto, but was too weak on full auto.

#10 MatthewTyson

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Posted 15 September 2010 - 10:45 AM

View Postgcw360, on 06 September 2010 - 07:12 PM, said:

You need to clarify what options you have with .25's at your field.  Typically you will chrono with .2's and then have the option to play with .25's.  Using .25's to lower the FPS is not cool.  The same amount of energy is delivered regardless of the drop in FPS and it is considered cheating the chrono to use .25's to drop the FPS in order to qualify. :gun:
I hate to derail the thread earlier, but this needs to be corrected.
.25s deliver MORE impact energy than a .2g bb, because of their momentum. source: Airsoft Trajectory Project (http://mackila.com/airsoft/ATP/)


On topic: I've been following the same topic on airsoft mechanics, they mentioned the possibility of weakening the spring in front of the flute valve in place of using different gas.

#11 gcw360

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Posted 15 September 2010 - 02:19 PM

View PostMatthewTyson, on 15 September 2010 - 10:45 AM, said:

I hate to derail the thread earlier, but this needs to be corrected.
.25s deliver MORE impact energy than a .2g bb, because of their momentum. source: Airsoft Trajectory Project (http://mackila.com/airsoft/ATP/)


On topic: I've been following the same topic on airsoft mechanics, they mentioned the possibility of weakening the spring in front of the flute valve in place of using different gas.

Hi MT:

I should have been clearer when explaining that I was referring to the amount of energy delivered as the BB exits the barrel and not the energy delivered as the result of momentum being preserved by the heavier BB down range.  Regardless the message is the same, using a heavier BB to cheat the chrono reading is wrong and people can get hurt.:gun:

#12 cjboi

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Posted 15 September 2010 - 02:21 PM

View Postgcw360, on 15 September 2010 - 02:19 PM, said:

Hi MT:

I should have been clearer when explaining that I was referring to the amount of energy delivered as the BB exits the barrel and not the energy delivered as the result of momentum being preserved by the heavier BB down range.  Regardless the message is the same, using a heavier BB to cheat the chrono reading is wrong and people can get hurt.:gun:

I totally agree. Cheater's can eat dirty nuts




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