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Service Advisory - MP7 Magazine BB Follower


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#1 Guest_allizard_*

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Posted 30 October 2009 - 01:35 PM

We have received a couple reports on MP7 Bolt Catch fail to lock when magazine is empty.  

The problem is due to damaging the BB Follower by continuously slamming/springing the BB Follower when magazine is empty.

MP7 Magazine
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This should be the correct position for BB Follower when BB is emptied in the magazine.
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When BB Follower is pushed all the way up, it will engage the lock to catch the bolt.
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When BB Follower is damaged.  It will caught outside of the mag well and will not push all the way up.
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Hence the Bolt Catch arm will not engage and fail to catch the bolt when mag is empty.
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Do not release magazine follower when the magazine is empty. Doing so will damage the magazine and magazine
follower.


#2 EmpireAirsoft

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Posted 08 January 2010 - 10:32 AM

So allowing the follower to spring upwards from the bottom of the magazine and slam into the top of the magazine causes it to deform over time because the metal is kinda soft to begin with correct?

#3 Spiggy

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Posted 14 January 2010 - 04:32 PM

View PostEmpireAirsoft, on 08 January 2010 - 10:32 AM, said:

So allowing the follower to spring upwards from the bottom of the magazine and slam into the top of the magazine causes it to deform over time because the metal is kinda soft to begin with correct?

It's not because the metal is kinda soft, but rather the spring is really-really powerful.  we opted to use a softer metal because it's cheaper to replace followers than magazine bodies and feed lips.  Had the material been hardened anything, the feed lip would probably tear through the mag body in some really awesome parts explosion.


This service advisory should apply to all models that use this type of locking mechanism.

#4 Vamp2269

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Posted 04 February 2010 - 12:34 PM

ha i avoid the issuse cause i never let it snap up the closest i came to doing that is letting it snap halfway and i only did it a couple of times. i used to have a crappy nonblowback pistol and i destroyed the mag by letting the folower spring up, and i was sure to not do the same with my mp7 mags.

#5 guitartilldeath

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Posted 25 February 2010 - 05:39 PM

how exactly do you preevent it from slaming onto the top? is this just saying "dont pull the spring down, be a dummy, then release it so it hits the top"?

#6 gcw360

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Posted 25 February 2010 - 07:05 PM

View Postguitartilldeath, on 25 February 2010 - 05:39 PM, said:

how exactly do you preevent it from slaming onto the top? is this just saying "dont pull the spring down, be a dummy, then release it so it hits the top"?
Yup!:gun:

#7 Vamp2269

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Posted 27 February 2010 - 10:29 PM

pretty much it

#8 vovi87

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Posted 30 July 2010 - 11:21 AM

Hi,


I've also bought an KWA/KSC MP7, and now I want to rebuilt it to fullautomatic mode,
because its an UMAREX Import Modell and this ones are changed to only semiautomatic.

So I've seen your site/forum concerning the MP7, and maybe you can help me to do this.

Do you have an idea, witch part UMAREX could be changed, that it just shoots semiautomatic ?

Or can you make a short instruction, and show the mechanic functions by selecting between semi an FA ?

Maybe some pictures can help too. :)



Thanks + kind regards

vovi87

#9 xKingSizex

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Posted 30 July 2010 - 04:08 PM

This thread is dedicated to the MP7 mag follower issue and is not a modification thread. Also, that model is designed to only shoot semi auto only in order to comply with the laws of that region. This forum is not for the use of this type of modification attempt.

#10 Kayl

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Posted 24 September 2011 - 07:06 PM

Where can I get more of these MP7 followers? Almost all of mine are damaged at this point, I need new ones. Warranty is voided, I need to buy new ones. I know how to fix this myself.

#11 Trevytrev

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Posted 25 September 2011 - 03:29 PM

i know that this is LOOSLEY related to this but is their any reason or way to damge the gun or magazine by racking the slide or releasing the slide catch on a usp?

#12 niko_gpsy

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Posted 26 September 2011 - 11:35 AM

View PostTrevytrev, on 25 September 2011 - 03:29 PM, said:

i know that this is LOOSLEY related to this but is their any reason or way to damge the gun or magazine by racking the slide or releasing the slide catch on a usp?
Not even close to being "loosely" related to this topic but it won't cause damage by doing that but it will cause wear and tear unnecessarily.

#13 xKingSizex

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Posted 26 September 2011 - 01:36 PM

We have the followers on order. Keep checking back with us for availability.

#14 SavageInsight

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Posted 11 March 2012 - 08:23 PM

So who *does* that?

   Step 1: Pick an *empty* magazine
   Step 2: Lock the bb feed push thingy (The magazine bb follower) down
   Step 3: Load the empty magazine
   Step 4: Click the follower in order to feed imaginary bbs

  If someone is used to loading several mags by clicking each first, then loading bbs, but misses one, I can understand, especially if they're the type to click the bbs into place as they load their MP7. Its still awkward.

I'm envious of anyone who can afford more than two or three magazines, and hope they're more clever about using them.

Edited by SavageInsight, 11 March 2012 - 08:23 PM.


#15 Trevytrev

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Posted 12 March 2012 - 04:53 PM

well, i brok my original magazine by just closing the bolt catch on the empty magazine. not releasing the follower for fun

#16 SavageInsight

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Posted 12 March 2012 - 06:12 PM

View PostTrevytrev, on 12 March 2012 - 04:53 PM, said:

well, i brok my original magazine by just closing the bolt catch on the empty magazine. not releasing the follower for fun

   I'll watch for that, thanks!

#17 jedisalad

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Posted 22 August 2013 - 09:11 PM

I disagree with your diagnosis of this problem.  I have a brand new mp7, purchased just a few days ago.  It came with 1 magazine.  No problems are observed at ALL using the stock bolt and the original magazine.  It has only had approximately 4 magazines shot through it at this time, and I have NEVER allowed the follower to snap closed.

I also purchased 4 additional KWA brand magazines and the KWA low-power bolt from Airsoft GI which arrived today.

Symptoms (fyi: these symptoms are 100% repeatable during both firing and manual operation):  

Stock bolt and stock mag: no issues, works fine

Stock bolt and new mags: works fine about 70% of the time, 30% of the time, the bolt fails to lock back.

Low-power bolt and stock mag: no issues, works fine

Low-power bolt and new mags: bolt fails to lock back 100% of the time


After visual inspection, I also first suspected the follower as the issue.  I have available a digital caliper so I decided to do some measurements to determine how the followers differed between the stock and new magazines.  Here are my findings:

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The height of the follower opening is .75mm shorter on the new magazines than it is on the stock magazines.  This difference is completely obvious to the naked eye and existed on ALL of the new magazines.

Measurements of the stock follower:

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Measurements of the new follower:

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So, as you can see, the new follower is .05mm shorter than the stock follower.  The side of the new follwer (the side that pushes up the bolt catch) is .06mm shorter than the stock follower, and the width of the new follower is .07mm thinner than the stock follower.  The entire new follower is smaller in every dimension than the original stock follower.  These differences were consistent among ALL the new magazines.

Although I took measurements of the stock bolt and the low-power bolt I was unable to find any differences of measurement of any interest and at this time can not explain why the stock bolt seems to work a bit better (being able to engage the bolt catch with the new mags some of the time).  However, due to the way the follower works, I do not believe the size of the follower to be part of the problem.  I believe the issue is directly related to the size of the opening at the top of the magazine not allowing the follower to raise high enough to engage the bolt catch.  The opening is very obviously taller on the original stock magazine.  This would explain why the new low power bolt works fine with the older stock mag.

For a final experiment I intend to file a very small amount of material from the top of the opening where the follower sits (see first photo) to allow it to raise another .07mm to .10mm higher on the magazine.  I have a feeling that will solve the issue and allow the bolt catch to ...   um...  catch.  I will update soon.

Edited by jedisalad, 22 August 2013 - 10:46 PM.


#18 jedisalad

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Posted 22 August 2013 - 10:16 PM

UPDATE!!!  FIXED!!!

I was able to fix the problem, but it ended up being an additional issue I hadn't seen yet but still related to my original thinking that the follower wasn't being allowed to raise high enough into the magazine to properly lift the bolt catch.

See photos below:

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My original thinking was that the opening on the magazine was too small to allow the follower to rise high enough to engage the bolt catch.  I filed a small amount of material from the top of the opening and reassembled the mag.  However the follower did not rise up into the newly created space and the problem persisted.  I realized that the top portion of the follower that rides in the channel on the front of the magazine was barely taller on all of the new magazines' followers than it was on the original stock follower.  After removing a small amount of material from this piece I conducted the following experiments:

Stock Mag, unaltered new follower, low pwr bolt: bolt does not catch 100% of the time

New Mag, stock follower, low pwr bolt: no problems, bolt catches properly

New Mags & Stock Mag, altered follower, low power bolt: no problems, bolt catches properly

The problem lies in the follower.  If the small rounded metal piece on the front of the follower above the release button is too tall (and I mean barely...  like .2mm) it will not allow the bolt catch of the follower (the piece on the side) to raise high enough to engage the bolt catch inside the gun and therefore the bolt will not lock back.  

I have tested this on all the mags now and this alteration works perfectly.  If this problem is widespread, KWA should probably recall the follower pieces, or at least offer to replace them.

#19 jedisalad

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Posted 22 August 2013 - 10:28 PM

Oops, should have included these photos also.  Probably the most important 2.  As you can see, the difference is pretty dramatic, .41mm difference.

New Follower (non-working):

Posted Image

Stock Follower (working):

Posted Image

#20 proverbialguy739

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Posted 22 August 2013 - 10:38 PM

chances are you got a lemon, as i doubt kwa would intentionally re-engineer the bb follower and only make a .5 mm change...
but yeah quality control issue it seems.




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