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Compression issues SR12?

sr12 compression

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#1 metalclash

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Posted 07 March 2013 - 06:35 PM

Hi all!

First I would like to say I love my SR12, I bought it in July of 2012, and it's been amazing in every single game I've played in.  However, out of boredom today I shot it and noticed with my eyes that the FPS dropped considerably.  The RoF and the accuracy are still top notch though.  When I went inside the gearbox (first time going into this gearbox since I owned it) I found that there was barely any compression at all.  It seemed to be the o ring around the piston head, so I just stretched it out and re greased everything inside.  Problem went away instantly.  The internals still looked beautiful, and I've put about 30k rounds through this already.

It was an easy fix but I was just wondering if this is normal for the gun to suddenly lose compression?  I do live in New Jersey, and it has been unbearably cold here compared to the summer where I did most of my playing.

#2 airsoftamateur32

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Posted 07 March 2013 - 06:38 PM

yea,it happens some times just a part that is normal matinence.My sr12 and m16 br both lost compression and then was repaired because of the oring.

#3 gcw360

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Posted 07 March 2013 - 08:29 PM

I live in NJ too.  Go Figure?  I opened a gun tonight (KM4A1) to do a FET install and some other choice upgrades and the FPS was all over the place.  It was because the o-ring had contracted.  I put a new o-ring in (after stretching) and the compression is awesome!

So, yes...it happens.

#4 metalclash

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Posted 07 March 2013 - 08:42 PM

Alright thanks guys, just wanted to make sure this was a normal wear and tear kind of thing rather than something more serious.

#5 niko_gpsy

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Posted 09 March 2013 - 05:30 AM

Replacing/ stretching piston head o-rings is just one of those maintenance things like re-greasing and relubing that needs to be done from time to time to maintain proper function.  It's like changing oil in your car. :)

#6 lester

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Posted 23 March 2013 - 05:52 PM

Will just streching the O ring fix bad compression, or does the O ring need replaced?  I ask because I have afive year old gen 1 M4 experiencing the same problem.

#7 vanevery

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Posted 23 March 2013 - 06:17 PM

View Postlester, on 23 March 2013 - 05:52 PM, said:

Will just streching the O ring fix bad compression, or does the O ring need replaced?  I ask because I have afive year old gen 1 M4 experiencing the same problem.

Get a brand new O-ring.
Stretch the brand new O-ring.
Don't stretch a used / worn out O-ring.

#8 lester

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Posted 23 March 2013 - 06:28 PM

I can get one at a hardware store right? If so, what size do I get? Thanks for the help.

#9 gcw360

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Posted 23 March 2013 - 06:36 PM

View Postlester, on 23 March 2013 - 06:28 PM, said:

I can get one at a hardware store right? If so, what size do I get? Thanks for the help.
#14 Danco. A ten pack is like $2.27 at Home Depot.

#10 niko_gpsy

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Posted 25 March 2013 - 04:45 PM

Make it a habit of changing out the piston head o-ring every time you open up your GB. They are so inexpensive and it will almost guarantee that a compression problem will not occur there.





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