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Bought A Used Kmp9, Fixing Her Up.


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#1 sniperelite7

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Posted 17 November 2011 - 07:37 PM

Found an old one and am presently fixing it up. No real problems so far, cylinder springs where mashed. Easy fix. Bolt doesn't return to battery every time, figured i'll just stretch out the spring that is the cause of that problem.

Overall the gun functions great. Noticed a couple of quirks though. Namely every so often when I push the bolt back into battery(occasionally it won't return into battery), sometimes pushing it forward causes the gun to discharge. Normal? Timing messed up? Another seperate occasion, I pulled the trigger and nothing happened, then probablly 10 seconds later it fired without the trigger being depressed. Again timing issue?

Hoping that these problems will dry up once I stretch out that spring.

In the mean time, the only problem that I can't seem to fix. The magazine likes to jam, no bb's I have will feed. These are quality ones at that. Excel .25s, airsoft elite .25s, and excel .20s are what i've tried none work, somewhere along the line in the stack they'll stop up. I ran some 1000 grit sand paper inside the channel to smooth out an imperfection. Too no avail. Any ideas to fix this? I'd rather not waste some 5000 bb's.

#2 gcw360

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Posted 17 November 2011 - 08:02 PM

Well, the spring #162 is causing the trigger/bolt issue.  A slight stretch is all you need to get the gun running smoothly.  Regarding the MAG, does the BB follower get hung up without BB's?  Also, does it lock down easily? I'm thinking that if it is not the BB's you are using, then the follower could be damaged from being released and allowed to "slam" up to the top.  It's an easy replacement if you buy a new part.

#3 gcw360

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Posted 17 November 2011 - 08:12 PM

View Postgcw360, on 17 November 2011 - 08:02 PM, said:

Well, the spring #162 is causing the trigger/bolt issue.  A slight stretch is all you need to get the gun running smoothly.  Regarding the MAG, does the BB follower get hung up without BB's?  Also, does it lock down easily? I'm thinking that if it is not the BB's you are using, then the follower could be damaged from being released and allowed to "slam" up to the top.  It's an easy replacement if you buy a new part.
PS - try KSC BB's to be sure it's the MAG.  They are designed for the gun and one way to eliminate issues when testing.

#4 sniperelite7

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Posted 17 November 2011 - 08:24 PM

View Postgcw360, on 17 November 2011 - 08:02 PM, said:

Well, the spring #162 is causing the trigger/bolt issue.  A slight stretch is all you need to get the gun running smoothly.  Regarding the MAG, does the BB follower get hung up without BB's?  Also, does it lock down easily? I'm thinking that if it is not the BB's you are using, then the follower could be damaged from being released and allowed to "slam" up to the top.  It's an easy replacement if you buy a new part.

Stretched it out, no matter how slowly I let the bolt go back into battery, the trigger can still be engaged, scratch that problem!

View Postgcw360, on 17 November 2011 - 08:12 PM, said:

PS - try KSC BB's to be sure it's the MAG.  They are designed for the gun and one way to eliminate issues when testing.

I'll keep that in mind about the ksc's. The follower locks and releases easily, and does not hang up anywhere. Though it looks kind of worn, no deformations, or major dings.

#5 gcw360

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Posted 17 November 2011 - 08:26 PM

Any chance you can send a picture of the follower.  One in the up position, one in the down?

#6 sniperelite7

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Posted 17 November 2011 - 09:34 PM

Attached File  Photo0512.jpg   116.09K   12 downloadsAttached File  Photo0513.jpg   137.94K   14 downloads



Taken from my "amazing camera", i'll try and see if anything can be done about the quality. Unless you can see what you need to see..?

Edited by sniperelite7, 17 November 2011 - 09:35 PM.


#7 gcw360

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Posted 17 November 2011 - 10:21 PM

It's hard to tell for sure, but I think the follower may be damaged.  It's late now I can try to post a pic of a new mag tomorrow and then you can compare with yours.

#8 sniperelite7

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Posted 18 November 2011 - 08:10 AM

Alright, perhaps a picture of how the bb's interact with the follower? Because they seem to be feeding fine when the first bb is staggered on the bolt catch side of the magazine. Though they seem to get hung up right around where the bolt catch bar triggers the bolt catch.

#9 niko_gpsy

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Posted 18 November 2011 - 08:54 AM

You could try taking the follower out and just buff down the side where it sits flat against the bb channel.  I had mine get stuck toward the middle of the mag and sanding that side of the follower down smooth solved that problem.

#10 sniperelite7

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Posted 18 November 2011 - 04:31 PM

Thanks for the help. The gun is feed great now!

#11 niko_gpsy

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Posted 18 November 2011 - 07:10 PM

Glad I can help.

#12 sniperelite7

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Posted 19 November 2011 - 11:05 AM

Now that the magazine is feeding I was able to test the performance with a full magazine. Single shots with delays between shooting(long delays). The gun refuses to blast through a full mag before emptying out. Granted its been cold around here, but i've heard that a kmp9 can go through three full magazines before needing to refill, that was at 30 degrees. According to a user. Another person reported 2 magazines in cold weather.

I'm barely getting one. Presently, following KWA's instructions to fill the mag until gas over flows. I haven't detected any leaks in the magazine, and the seal on it looks good. Its been cleaned and lubricated properly and chrono'd at around 380fps last I checked. What would be the parts that would affect gas efficiency in such a dramatic way?

About the only thing that I could think of would be that the loading nozzle appears slightly malformed. Having a raised edge on the upper part of the nozzle. Though the difference in dimension from that and a brand new nozzle are hardly noticeable. I wouldn't have thought that it would have made much of a difference.

#13 gcw360

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Posted 19 November 2011 - 03:25 PM

Is the can of GG new?  The can can feel like it's got gas in it but can have trouble filling any mag, any brand, if it's low and cold combined.

Also, what brand is it?  I have had many issues with Power Green gas.  It's the one you need to screw on an adapter for.  I won't use it anymore and the store I tech for won't carry it anymore.

#14 sniperelite7

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Posted 19 November 2011 - 07:33 PM

Actually its a can of propane. Left over from an old kjw1911. Didn't use a whole lot of it at the time.

#15 gcw360

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Posted 19 November 2011 - 07:41 PM

Well, the can could be close to empty and not providing enough pressure to fill.  The MP9, and all the KWA GBB guns, are tuned to run on green gas.  I recommend that you buy some and reevaluate the gun.

#16 sniperelite7

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Posted 20 November 2011 - 05:58 PM

View Postgcw360, on 19 November 2011 - 07:41 PM, said:

Well, the can could be close to empty and not providing enough pressure to fill. The MP9, and all the KWA GBB guns, are tuned to run on green gas. I recommend that you buy some and reevaluate the gun.

Will attempt too, have to check the local airsoft store. In the meantime, I had a second fresh can of propane laying around and popped it on. Was able to get through a magazine and a half before it died down. Temperature around here is about  52 degrees F if thats any indication on how it may be doing?

#17 gcw360

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Posted 20 November 2011 - 06:17 PM

Sounds like all is well!

#18 sniperelite7

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Posted 20 November 2011 - 07:16 PM

View Postgcw360, on 20 November 2011 - 06:17 PM, said:

Sounds like all is well!

Huh really? Thats great I guess. though alot of the reports I saw where saying that you would get more out of a magazine.

#19 gcw360

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Posted 20 November 2011 - 08:40 PM

At 52 degrees?  I once tested an MP7 mag at 42 degrees.  I was able to empty the mag but not much more.  The MP9 mag has a smaller volume and fires in the 380 range on a warm day.  I would expect 2 mags then.  But at 52 degrees...not thinking so, but I could be wrong.

#20 sniperelite7

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Posted 20 November 2011 - 08:42 PM

Ha! Alright man, i'll concede to that. Thanks again!




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