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Piston Not Locking Back All The Way?


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#1 Nitemare

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Posted 21 May 2012 - 03:59 PM

I cleaned my gun the other day and noticed that since then, sometimes the piston doesn't lock back all the way when  the mag is out of ammo. It'll end up like this:

Posted Image

I'm not sure what the issue is. I lubed it at the cylinder where the manual said to, but not on the sides of the piston where it travels along and contacts the bolt body (more particularly the piston stop). When I open the receiver and manually move the piston, it seems to be getting caught here because the plastic is a little bit rough (circled black):

Posted Image

Posted Image

I tried putting some heavy weight silicone on a q-tip and lubing the piston all around, and more particularly in the area where it is getting caught on the piston stop.

After dry firing on semi a few times (so the bolt would lock back each time), it seemed to have been fixed. As soon as I went full auto for a few rounds then let it lock back, it got stuck again on both semi and full auto. I'm not sure if it was because the mag only a had a little bit of gas or what. Should I try sanding down that rough plastic area or does it serve a purpose?

#2 R_King91303

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Posted 21 May 2012 - 04:17 PM

Interesting, the circled thing almost looks like a serial stamp or teeth. Is the rough patch only on that one side?


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#3 Nitemare

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Posted 21 May 2012 - 04:38 PM

I believe it says 4.9.1, but yes that's the only rough spot. I spoke to a KWA tech for awhile and they suggested that the gun needs wear-in time. While this makes sense, I'm not sure if I entirely agree because it wasn't doing this the other day. I've cycled it close to 1000 times already. He also suggested that it may be because the mag was fairly empty and a lot of force is needed to cycle the gun. While I agree with this, the piston has a spring to pull it back, so it's clearly being stopped by something.

#4 Outlaw1995

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Posted 21 May 2012 - 05:02 PM

I've encountered the same problem, it should go away after a few thousand rounds like the KWA tech said. After putting 4000 rounds through mine, the problem is barely there anymore. There is a nice vertical scratch inside my receiver though, perhaps the plastic nozzle is getting caught on that... another note: my bolt lock doesn't always engage on the last shot, and it was solved by running the gun through its paces a little more. Shoot somewhere near 5000 rounds and the gun should be fine.

#5 Nitemare

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Posted 21 May 2012 - 05:33 PM

Thanks for the input Outlaw. Will help me sleep better tonight ;)

#6 dino325

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Posted 22 May 2012 - 02:33 AM

I'm glad to hear that the solution is simple, as I haven't run across this yet. I'm just wondering how some of you have put 5000 rounds through your guns already! Geez, that's 125 magazines! I obviously need to do some catching up ;-).. Happy Hunting...

#7 dazdarren

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Posted 22 May 2012 - 04:23 AM

There is actually a C clip on the other end of the piston.
The piston is connected by a spring and you need the c clamp to allow it to return to position.

#8 Outlaw1995

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Posted 22 May 2012 - 05:22 AM

View Postdino325, on 22 May 2012 - 02:33 AM, said:

I'm glad to hear that the solution is simple, as I haven't run across this yet. I'm just wondering how some of you have put 5000 rounds through your guns already! Geez, that's 125 magazines! I obviously need to do some catching up ;-).. Happy Hunting...
I've probably shot more than that, considering I went through a bag and a half of bbs....

#9 dino325

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Posted 25 May 2012 - 08:06 PM

View PostOutlaw1995, on 22 May 2012 - 05:22 AM, said:

I've probably shot more than that, considering I went through a bag and a half of bbs....


Geez, how many mags are you running. I'm up to 5 now. Thinking ill top out at 8 but who knows ;-)..

#10 Outlaw1995

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Posted 25 May 2012 - 08:07 PM

View Postdino325, on 25 May 2012 - 08:06 PM, said:



Geez, how many mags are you running. I'm up to 5 now. Thinking ill top out at 8 but who knows ;-)..
At the time, I had only one magazine. Now I have two... hoping to have 4 by the end of the month, and 6 to complete my load out.




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