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HUGE FPS drop after opening gearbox

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#1 Rex3453



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Posted 14 January 2009 - 11:07 PM

Before I begin, I know my warranty is voided, and I do know that you're not supposed to do this, but I upgraded my gearbox with the following:

-Systema Duracon Piston Head
-Prometheus V2 Spring Guide
-Systema Air Nozzle

Others that are not related to gearbox:
-TM Hop up
-Firefly Bucking (Soft)
-Prometheus 6.03 407mm barrel

Okay, now onto my problem, after opening my gearbox to install the following above, I installed all of the stuff obviously, then closed the gearbox like you should, it was ALL perfect, compression was perfect, etc.

...but one problem, after shooting the gun, I noticed that my FPS dropped considerably, now 2 hours before I even opened up the gun, I went outside and did a poor man's chrono, shot through the bottom, dented the top, shot through both sides, etc. all pointing to me still having around 400 FPS, after opening and closing the gearbox, it would not even dent the side of the coca cola can, and of course it would not dent the bottom.

Now, to go into further detail about this, after about 75 feet, or 50 feet, the BB starts to drop to the ground instantly, even with the hop up turned off, not like it used to be, go 200 feet and then drop to the ground.

I took apart the gun, and I knew instantly it had to be the compression, I reset the gear timing so the sector plate on the sector chip was at the 3 o' clock position, I did it when it was set to the 1 o' clock position, 2 o' clock, heck even 6 o ' clock after the sector chip released the piston....it all gave me the same results.

I replaced all of the upgrades with stock parts, compression was good, everything was fine, I went to shoot the gun outside, same exact results, even without the upgrades.

Also, the things I checked before putting the gearbox into my lower receiver and putting the gun back together:

-Tappet plate: I pushed it back with my index finger, the air nozzle went back like it should, and sprang forward, it is normal
-Tappet plate spring: yes it's on there
-Battery: fully charged (btw it's a 11.1v lithium polymer battery with an output of 15A IIRC)
-Anti-reversal latch: works perfectly
-Gears: I moved them all, and everything moves fine
-Spring: I did NOT compress it over night, even if I did, I would not be seeing such a huge difference in performance

I seriously do not know what is wrong with my gun, I'm about to send it into an airsoft shop and just pay for them to repair it, or send it to KWA to repair it.


#1: I have the upper receiver off, I pull the trigger and the air nozzle springs forward, and back...it locks in place and does not go forward


#2: I pull the trigger again, air nozzle springs forward and stays there


#3: Right after I open the gearbox, I do not touch anything and leave it as is, besides the spring and spring guide, obviously


#4: How I set the gears before closing the gearbox


Thanks in advance for helping me, this problem has been with me since last Sunday, and it is really irritating me, I've tried doing hundreds of things, and I can NOT find out what's the problem.

EDIT: Forgot to mention, it's not the hop up unit and the bucking, those are set correctly.

Edited by Rex3453, 14 January 2009 - 11:09 PM.

#2 Guest_allizard_*

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Posted 15 January 2009 - 03:03 AM

You are welcome to send it back to us for a repair.  It's $35 to start with the out of warranty service plus shipping.

#3 Rex3453



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Posted 15 January 2009 - 06:36 AM

Yeah, thanks, I'll probably do that.

Every airsoft forum I go to does not know the reason why it's doing this.

#4 Rex3453



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Posted 15 January 2009 - 06:00 PM

Okay, after opening my gearbox and cleaning the inside of the gearbox, I noticed that there were shavings of something on the path where the tappet plate lays, thus causing something wrong.

I then notice that on one side of my piston, it was chipped VERY badly to the point where it broke and pieces were in my gearbox, so I had to go and take them all out.

I'm blaming you KWA!

Not really, it's not a big deal at all, simple fix; also it was probably my fault for doing that...some how.

But yeah, problem = solved.

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