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Help me with my MP9, i have to pull the charging handle back each time i fire

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#1 Icurblud

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Posted 02 October 2013 - 01:15 PM

My mp9 just started acting up.  It only allows me to fire 1 bb. Then it makes me recock it. Then fire 1 bb, then again cock it and so on.  Whats up.

#2 gcw360

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Posted 02 October 2013 - 02:41 PM

View PostIcurblud, on 02 October 2013 - 01:15 PM, said:

My mp9 just started acting up.  It only allows me to fire 1 bb. Then it makes me recock it. Then fire 1 bb, then again cock it and so on.  Whats up.
Is the bolt cycling with each shot?

#3 Icurblud

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Posted 02 October 2013 - 03:18 PM

gcw, i should just message you directly on any questions i have.  your always 1st to act on every thread.  for that i thank you.

yes the bolt completly cycles.

#4 gcw360

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Posted 02 October 2013 - 03:25 PM

View PostIcurblud, on 02 October 2013 - 03:18 PM, said:

gcw, i should just message you directly on any questions i have.  your always 1st to act on every thread.  for that i thank you.

yes the bolt completly cycles.
Thank you.  While it's fine to PM me, putting the thread up will hopefully help others.  

There could be a few reasons for your issue.  Perhaps there is not enough gas pressure to completely cycle the bolt? This could be from a partially filled mag, or perhaps the piston seal is damaged.  I'm guessing that's not it but you never know.

Another cause could have something to do with the hammer itself.  This is where I would focus.  When you cock it by hand, does it seem rather hard to do?

#5 Icurblud

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Posted 02 October 2013 - 05:36 PM

I have 5 mags and they all act the same, so i am going to rule out  a gas issue.   When i cock it back its normal, not hard nor easy, normal.  Bolt moves completly back and cycles fully when fired.   I was thinking something to do with the hammer or a spring that is supposed to keep the hammer back.

#6 gcw360

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Posted 02 October 2013 - 06:33 PM

View PostIcurblud, on 02 October 2013 - 05:36 PM, said:

I have 5 mags and they all act the same, so i am going to rule out  a gas issue.   When i cock it back its normal, not hard nor easy, normal.  Bolt moves completly back and cycles fully when fired.   I was thinking something to do with the hammer or a spring that is supposed to keep the hammer back.
Try this, take a flat screwdriver and stretch spring part # 162.  Don't stretch it too much.  By putting the screwdriver between the coils and giving it a twist you may get the result you need.  If that doesn't fix the issue we can focus on the hammer.

#7 Icurblud

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Posted 02 October 2013 - 07:24 PM

I will try that.  
http://kwausa.com/fi...S02V01_KMP9.jpg

Edited by Icurblud, 02 October 2013 - 07:24 PM.


#8 Icurblud

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Posted 03 October 2013 - 09:58 AM

Looks like that did the trick.  Could see anything wrong but after doing what you suggested its firing on all cylinders.

#9 gcw360

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Posted 03 October 2013 - 05:31 PM

View PostIcurblud, on 03 October 2013 - 09:58 AM, said:

Looks like that did the trick.  Could see anything wrong but after doing what you suggested its firing on all cylinders.
:tsuki: Happy to help.  What was happening is that the bolt wasn't being allowed to reset all the way.  Stretching that spring fixes the issue.

#10 PJ-P09

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Posted 19 December 2013 - 02:50 PM

Hi all, today i "repaired" a friend's KMP9 with the same problem, his issue was that by any reason the bolt carrier didn't close 100% with the hopup chamber so the disconnector #153 sometimes didn't release the hammer, but when he cocked it again the bolt make the full travel, closing the chamber and firing 3-7 times more and again stoped. If you dont focus on the bolt you never see that is not fully clossed, maybe it's at 95% like this:
Open
Posted Image

Close

Posted Image

The solution:

1.- In his model (compared to mine) the bolt main spring #69 seems to be not strong enough so we extended it carefully

2.- The nozzle return springs were pretty much smashed, so replaced them with new ones
(This ussually produces jams and block the bolt in  a none firing possition)

3.- In his nozzle (Dytac version -link-) the inner diameter by some reason, was bigger than usual and leaks lots of gas while firing, producing a very very low gas efficiency (less than 1 full bb mag per gas charge) so we replaced it by a new one also from Dytac.

Now it fires perfectly every bb in the mag with an efficiency of about 2.3 bb loads per gas charge

BTW i recomend the WiiTech Nozzle and Nozzle guide kit, produces much more gas efficiency and ROF
-Review here-

Edited by PJ-P09, 19 December 2013 - 03:21 PM.






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