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Gun Hard To Cock, Very Little Gas On Firing.


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#1 dobey

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Posted 16 August 2011 - 04:09 PM

I just ran into this problem on a well used mp9, the gun is stiff to cock and when fired it puffs out the bb and a little bit of gas.  

I dove into it and after poking around for a little bit I found the problem, the cast in pivot pin on the hammer broke on the ejection port side.  It was tough to find because the hammer cocked fine by hand (meaning I pulled it back with my finger to cock it and fire it) but it would rotate enough when fired to barely hit the gas valve.

I am just going to drill it out and install a steel roll pin but this is something to keep an eye out for, and was difficult to see that it was broken.

Posted Image

#2 gcw360

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Posted 16 August 2011 - 06:26 PM

Good post thanks.  About how many rounds do you think have gone through the gun? :gun:

#3 dobey

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Posted 17 August 2011 - 03:27 AM

I would guess in the 10,000 to 20,000 round range.

#4 dobey

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Posted 17 August 2011 - 07:30 AM

Got it all fixed and working again.  Drilled out a hole in the hammer and made a new piece from steel to replace the broken off part:

Posted Image

Here it is with the new part pressed in, and the old broken piece next to it, works like a charm:

Posted Image

#5 gcw360

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Posted 17 August 2011 - 06:33 PM

You are a very cool contributor....:thumbsup:

#6 BLAH12431

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Posted 11 February 2012 - 02:02 PM

How hard is it to take apart the gun down to the hammer? I'm wondering since my hammer just broke too.

#7 dobey

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Posted 18 February 2012 - 06:27 AM

It wasnt very difficult, about the same as working on an aeg gearbox.  If you are comfortable with that then go for it.

#8 BLAH12431

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Posted 18 February 2012 - 03:07 PM

Thanks for the reply. I think I'll just send it in since I don't feel to comfortable with doing something like this.

#9 vilerk

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Posted 20 February 2012 - 11:56 PM

I did a similar fix to my hammer, but with a roll pin instead.  After a couple of hundred of rounds, the other side snapped.  I'm kind of hesitant to buy a replacement hammer now.  Would the same thing happen again?

#10 dobey

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Posted 21 February 2012 - 06:11 AM

Mine is still going strong since this fix, I would definitly try a new one becuase I see plenty of these at the field that never had this problem.

#11 REDARMY

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Posted 22 February 2012 - 03:55 PM

This has just happend to me. Both the arms broke though. I to am a little hesitant to buy a new hammer seeing that it has happend to multiple people.

#12 gcw360

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Posted 22 February 2012 - 05:07 PM

Understand that KWA enhances the design of parts that fail.  This is a very good chance that ir won't happen again.

#13 BLAH12431

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Posted 23 February 2012 - 01:03 AM

Honestly I'm not sure whether or not I want to go through the trouble of sending my gun in, I might just try to sell it for cheap since its broken.

#14 apacifico3

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Posted 23 February 2012 - 10:18 AM

I'll take it off your hands... ^_^

#15 BLAH12431

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Posted 24 February 2012 - 11:10 PM

View Postapacifico3, on 23 February 2012 - 10:18 AM, said:

I'll take it off your hands... ^_^
How much? :huh:

#16 gcw360

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Posted 25 February 2012 - 07:56 PM

Let's stop right here.  There is no selling in the KWA Forums.  Any further discussion related to sales will be deleted.

#17 apacifico3

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Posted 25 February 2012 - 08:18 PM

Sorry... :unsure:

#18 gcw360

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Posted 25 February 2012 - 08:21 PM

OK

#19 frostysubxero

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Posted 14 January 2013 - 06:04 PM

Thanks for this, I was trying to figure out what was wrong with mine (I was comparing my working MP9R to mynon-working MP9). As soon as I pushed my hammer down on my MP9 I could tell it was broken.




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