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KWA SR10, Low FPS

SR10 low fps KWA Fix Help

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#1 schuhbacca

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Posted 18 February 2013 - 10:10 AM

Hello forum users,
I purchased a kwa SR10 about a year ago from a local licensed retailer. I never had the gun chronoed or have done it myself about a month ago. Usually I just play with friends but when I had the gun chronoed at this even the reading came back as around 330 with a .20 gram bb. Everything is stock and the only thing I have ever done is take apart the hop up and clean it and clean the barrel. I know the hop up could be an issue but I have taken it apart again to see if the nub or bucking was damaged or missing but both seemed fine. I am wanting to know some of your thoughts as to what it could be. I just want to get an idea of some possible causes before I either send the gun in or open up the gear box myself. Any suggestions would be greatly appreciated. Thanks in advance.

#2 nbv386

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Posted 18 February 2013 - 10:35 AM

You might just need a new #14 danco o-ring from Home Depot. Or it could be your cylinder head o-ring. Or check if your air nozzle is damaged.

#3 gcw360

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Posted 18 February 2013 - 10:48 AM

There a re a number of things that can cause this:
  • Damaged or worn bucking
  • Piston o-ring
  • Compressed spring
  • Cracked cylinder head
  • Stripped piston
Note:  If it's the cylinder head or piston, they will fail quickly, make themselves known, and need replacing.

Also, make sure the hop-up travels fore and aft....basically, when you push it forward it springs back into place (there is a spring on the top of the hop-up unit that causes this).  If this doesn't happen properly you can have a big drop on FPS.  It's an easy fix though.

#4 schuhbacca

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Posted 18 February 2013 - 11:54 AM

Thank you for the quick responses. Now if it isn't the hop up of something like a cracked cylinder head or stripped piston which are easily visible how would one be able to tell what the issue is. Such as a bad o ring or compressed spring?

#5 gcw360

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Posted 18 February 2013 - 03:18 PM

View Postschuhbacca, on 18 February 2013 - 11:54 AM, said:

Thank you for the quick responses. Now if it isn't the hop up of something like a cracked cylinder head or stripped piston which are easily visible how would one be able to tell what the issue is. Such as a bad o ring or compressed spring?
You would need to open the gun and test the compression and inspect the spring.
Also, I assume you are testing with the hop-up off and using .20 BB's correct?

#6 schuhbacca

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Posted 18 February 2013 - 03:38 PM

That is correct and I just got home from work and did as you recommended and pushed on the hop-up bucking with a small screw driver and it seemed to very hard to push forward. I am not sure if that is normal or is that the reason for the drop in FPS?

#7 niko_gpsy

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Posted 18 February 2013 - 03:52 PM

Or you could've left your guns with the spring compressed when not in use.  Did you remember to always blank fire a few rounds to decompress the main spring?  If this is the case you will need to replace the spring if you desire a higher FPS and take that opportunity to inspect, clean and relube all the parts that requires it.  And also change out the piston head o-ring while you are at it.

#8 schuhbacca

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Posted 18 February 2013 - 04:08 PM

I am usually pretty good with decompressing it but you can never count it out that you forgot it. I will just have to take the gear box apart to check and see and maybe also replace the hop up.





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