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G36c FPS very low


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#1 TwoTonedSocks

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Posted 26 July 2014 - 05:59 PM

I've had a low FPS issue with my G36c for probably a year. It gets ~260FPS with the standard 247mm barrel, and ~300FPS with a 395mm tight bore. I've changed the piston O-ring and the compression is is good. I can't push it all the way down, even if I try hard. I've replaced the hop up unit and bucking, but the problem still exists. The only thing I can think of, that could cause the problem, is the spring. I would like ~350FPS with the 247mm barrel, and ~390FPS with my 395mm barrel. Can you help me get the right spring for the job?! Or suggest other possible issue. Thanks!

#2 gcw360

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Posted 26 July 2014 - 07:35 PM

What bucking are you using, what BB's are you testing with, and is the hop-up turned off during chrono?

#3 TwoTonedSocks

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Posted 26 July 2014 - 07:56 PM

I'm using the KWA 2G bucking, the KWA .20g bbs, and the hop-up is about half way, but other times off. I'll re chrono tomorrow, when there's sun, with the hop-up confirmed completely off. But even if it was on all the way, I still believe the FPS is still too low.

Edited by TwoTonedSocks, 26 July 2014 - 08:00 PM.


#4 gcw360

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Posted 26 July 2014 - 08:01 PM

View PostTwoTonedSocks, on 26 July 2014 - 07:56 PM, said:

I'm using the KWA 2G bucking, the KWA .20g bbs, and the hop-up is off.
If your FPS is that low I think it is something other than the spring.  Inspect the cylinder head for cracks and the piston for stripped teeth.

Do you know what cylinder you have?  Where is the port?  Can you post a pic?

#5 TwoTonedSocks

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Posted 26 July 2014 - 08:35 PM

View Postgcw360, on 26 July 2014 - 08:01 PM, said:

If your FPS is that low I think it is something other than the spring.  Inspect the cylinder head for cracks and the piston for stripped teeth.

Do you know what cylinder you have?  Where is the port?  Can you post a pic?

I have everything stock, except the selector plate. I just looked and nothing is cracked, and teeth are all there. I just checked the compression, and it was solid. The cylinder head popped out before any air passed through.

I'm trying to post pictures, but they're too large.

#6 TwoTonedSocks

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Posted 26 July 2014 - 08:39 PM

.

Edited by TwoTonedSocks, 26 July 2014 - 09:42 PM.


#7 TwoTonedSocks

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Posted 26 July 2014 - 08:40 PM

.

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#8 gcw360

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Posted 26 July 2014 - 08:55 PM

View PostTwoTonedSocks, on 26 July 2014 - 08:40 PM, said:

.
OK, the hop-up is where I would look next.  Is it (the unit) properly seated against the nozzle?  Also, here is a trick:
  • Chrono the gun for a baseline FPS
  • Take a pencil and from the muzzle end gently push the inner barrel back towards the upper receiver
  • Re-chrono
What is the change in FPS?

Given your apparent knowledge, my guess is that asking if the inner barrel has been cleaned is not warranted.  That said, I have had dirty inner barrels reduce the FPS by as much as 60 FPS.  By the way, it's not the cylinder....thank you for the picture.

Let me know of the pencil test does anything.  If that doesn't change the outcome you could try a new spring....but I'm really not convinced that is the issue.

#9 TwoTonedSocks

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Posted 26 July 2014 - 09:45 PM

I put it back together, and there seems to be a very slight gap between the nozzle and the hop-up. A piece of paper can easily slip in between. I don't know if that's normal or not.

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#10 TwoTonedSocks

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Posted 27 July 2014 - 12:30 PM

I re chronoed to day: same results. The pencil trick worked, it brought the fps up by about 40FPS, but only for one or two shots, and then it went back down.

#11 gcw360

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Posted 27 July 2014 - 01:29 PM

View PostTwoTonedSocks, on 27 July 2014 - 12:30 PM, said:

I re chronoed to day: same results. The pencil trick worked, it brought the fps up by about 40FPS, but only for one or two shots, and then it went back down.
Is the spring in place on the outter barrel in fron of the hop-up unit?

#12 TwoTonedSocks

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Posted 27 July 2014 - 02:28 PM

View Postgcw360, on 27 July 2014 - 01:29 PM, said:

Is the spring in place on the outter barrel in fron of the hop-up unit?
Yes it is

#13 gcw360

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Posted 27 July 2014 - 02:42 PM

Hmmm, anyone else have ideas?

#14 BLATEY

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Posted 27 July 2014 - 04:31 PM

I believe it's the small space in between the air nozzle and the hop up. You need to somehow connect both to make the air seal better.
I don't work with g36 guns but I belive that's your issue. I believe you should also try a different bucking for a better air seal, prommy purple maybe?




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