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M11 Venting Gas


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#1 Riflewizard

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Posted 17 September 2010 - 05:28 PM

So, i just got a KWA Mac11 NS2 in a trade.

The gun has an issue with venting it's gas.

There are 5 magazines, and they seem to vary in degree of functionality, some vent instantly, others fire for a little while.

I am low on propane in my can if that is a factor.

I have opened it up and lubed it and it looked to be in order.

It just vents like crazy right now and only shoots a few BB's until venting occurs, making it pretty much unusable.


Any suggestions?

#2 RexRocker AEG Dr

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Posted 17 September 2010 - 06:20 PM

View PostRiflewizard, on 17 September 2010 - 05:28 PM, said:

So, i just got a KWA Mac11 NS2 in a trade.

The gun has an issue with venting it's gas.

There are 5 magazines, and they seem to vary in degree of functionality, some vent instantly, others fire for a little while.

I am low on propane in my can if that is a factor.

I have opened it up and lubed it and it looked to be in order.

It just vents like crazy right now and only shoots a few BB's until venting occurs, making it pretty much unusable.


Any suggestions?


I have two:

1) Get your money back

2) Send it to KWA for a full repair

I have a question though, did you test fire it before the purchase?

Edited by RexRocker AEG Dr, 17 September 2010 - 06:21 PM.


#3 Riflewizard

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Posted 17 September 2010 - 07:16 PM

I'm trying to fix it myself, and no but i was assured it worked properly, i'm contacting the seller about it now.

Anyways... I think i have found the source of my issues:


Posted Image

Here is a picture of it jamming or whatever. The bolt is at half-cock position but the nozzle is far forward and almost a bit wedged in/hard to pull back.

Why is this occuring? It doesn't happen every round but rather every few, at least. If i manually cock it back at that point the gun would proceed to fire correctly.


The gun, when set like above, makes a weird noise and only partially blows-back, not enough to catch the sear so it will shoot a short burst of gas that varies from just dry-firing/wasting some gas, to dumping the whole magazine's load of gas out at once.

Edited by Riflewizard, 17 September 2010 - 07:22 PM.


#4 cjboi

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Posted 17 September 2010 - 09:42 PM

is your nozzle getting stuck in the hop up? make sure the screws are tight and not loose.

#5 Riflewizard

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Posted 17 September 2010 - 10:07 PM

Which screws?

#6 cjboi

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Posted 18 September 2010 - 12:41 AM

screw for your bolt or also check the pin for your nozzle that holds the flute valve.

#7 Riflewizard

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Posted 18 September 2010 - 05:07 PM

The issue seems to be the cylinder not returning, the springs aren't strong enough to pull it backwards.

#8 Riflewizard

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Posted 18 September 2010 - 07:07 PM

Okay so a bit more of an update: Seller says he got a new nozzle/cylinder after the original malfunctioned. Said he got it from the KWA pro shop.

Also what seems to be happening is the piston head seal is creating a lot of resistance in the cylinder.

Edited by Riflewizard, 18 September 2010 - 07:24 PM.


#9 gcw360

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Posted 18 September 2010 - 07:24 PM

Frankly to me that is ire

View PostRiflewizard, on 18 September 2010 - 07:07 PM, said:

Okay so a bit more of an update: Seller says he got a new nozzle/cylinder after the original malfunctioned. Said he got it from the KWA pro shop.

Frankly, to me that is irrelevant. Your gun i malfunctioning and I suggest you press the seller for a resolution.:gun:

#10 Riflewizard

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Posted 18 September 2010 - 07:25 PM

Ignoring the fact i have gotten jipped more or less, the fact of the matter is this gun is gonna get fixed, and if i can do it myself i'll opt for that.


I also heavily lubed the cylinder with silicon oil and the gun is working more reliably now. Hopefully this was the fix and it will wear in with time.

Edited by Riflewizard, 18 September 2010 - 10:12 PM.


#11 Riflewizard

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Posted 19 September 2010 - 07:41 PM

Okay so as i thought the lube was simply blown out of the system after the first mag and a half, and now it's back to it's old self.

Either the cylinder or piston head seal is at fault here. the Cylinder/loading nozzle has a MK11 marking on it and the seal is green but clearly puts too much pressure on the walls of the cylinder except when coated with silicon oil.

Edited by Riflewizard, 19 September 2010 - 07:42 PM.


#12 cjboi

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Posted 20 September 2010 - 09:05 AM

I think you may have the wrong cylinder installed. You can put some silicone oil, but not too much.

#13 Riflewizard

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Posted 21 September 2010 - 10:35 PM

I dont think that is the issue. Can anyone else chime in with some ideas? I'll be testing some components using a friend's MAC this week sometime so i should be able to find whats up.

#14 cjboi

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Posted 22 September 2010 - 04:06 AM

remember there's also KSC m11a1 system 7 made in japan. Those cylinder are thinner and only made for HFC134 gas and both marked with mk11. The m11 system 7 Japan parts are different from system 7 Taiwan version. What if the seller lied and told you he bought it from here, but really he bought it from some website.

#15 Riflewizard

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Posted 14 October 2010 - 02:21 PM

Okay guys, been a while, but update.
Borrowed a friend's MAC.
I swapped our cylinder seals (the green piston head bit)
His gun works fine with my seal.
Mine vents gas instantly on the first shot. Gas even shoots out of the two stock tang holes! (dont have stock installed)




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