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KWA LM4 PTS - PMag Leak

LM4 PTS PMag leak

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#1 General Pickle

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Posted 05 May 2013 - 10:18 PM

Hey guys, the video I made pretty much explains the problem but in case you can't view the video I'll type it up.



A few of my PMags have been leaking, which wasn't a huge issue since most of them could be fixed with a new o-ring I had laying around or just tightening things, but two of my mags are leaking from the gasket that seals the base plate and the shell together. I've tried using a silicone-in-a-tube type solution to seal the unruly spot but that didn't work. Sadly since it's not a readily available part found in hardware stores this is a little more difficult to fix. My last resort is to buy new gaskets, but of course that would be an easy way of doing it. I'm looking for a cheap way to do this myself so that I can do it in the future in case it happens again. Plus, I'm an engineering student, so I can't help but try to do it all myself :P Any suggestions or advice is much appreciated!

#2 akiraspeedstar

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Posted 06 May 2013 - 06:16 AM

Did you only use gasket maker at the front portion of the base or did you use it all the way around the base? Also did you let it dry for 24 hours before gassing it?

#3 General Pickle

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Posted 06 May 2013 - 08:14 AM

I went ahead and did it all around the base just to be sure, and there's a possibility that it didn't have a chance to fully dry before I gassed it. When I opened it again the goo was still pretty soft but I've used that stuff before and it generally doesn't get much harder. Maybe a more liberal application of it with more dry time would be more effective? Last time I tried it I applied the goo and then assembled the mag so that it would take the shape of the area needed, but maybe that prevented it from being thick enough to seal the gap.

#4 akiraspeedstar

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Posted 06 May 2013 - 09:27 AM

Well for my mags I cleaned it with alcohol, applied silicone over and under the gasket and immediately closed it up. Letting it firm up a little isn't a bad idea either though it wasnt necessary for me. I then let it sit for 24the hours and then filled it with gas and the leaks were gone and have yet to return.

Edited by akiraspeedstar, 06 May 2013 - 09:29 AM.


#5 WTF?Shane

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Posted 06 May 2013 - 11:18 AM

I gave it a quick spurt of propane after assembly to put some pressure on the RTV and hopefully get it to seal better. In theory it sounds like it works.

#6 General Pickle

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Posted 06 May 2013 - 02:55 PM

View Postakiraspeedstar, on 06 May 2013 - 09:27 AM, said:

Well for my mags I cleaned it with alcohol, applied silicone over and under the gasket and immediately closed it up. Letting it firm up a little isn't a bad idea either though it wasnt necessary for me. I then let it sit for 24the hours and then filled it with gas and the leaks were gone and have yet to return.
Maybe that was my issue, being that I didn't clean it very well before hand and I didn't remove the gasket from the base plate, I think you're onto something there. I'll give that a shot and see what happens, thanks!

#7 netpoc

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Posted 06 May 2013 - 06:12 PM

Use some thick silicone grease on the inside and outside of the "o-ring," and then some in the corners of the reservoir (not the baseplate, the reservoir where the baseplate goes into).

Edited by netpoc, 06 May 2013 - 06:13 PM.


#8 BoobieM4H

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Posted 06 May 2013 - 08:44 PM

And be sure not to over torque the two screws on the bottom. Doing so will cause the screws to "pull" out the bottom base and separate the base from body  and break your seal..very bad design in the lm4 pmags imo

( o Y o )

Edited by BoobieM4H, 06 May 2013 - 08:45 PM.


#9 General Pickle

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Posted 06 May 2013 - 08:48 PM

View PostBoobieM4H, on 06 May 2013 - 08:44 PM, said:

And be sure not to over torque the two screws on the bottom. Doing so will cause the screws to "pull" out the bottom base and separate the base from body  and break your seal..very bad design in the lm4 pmags imo

( o Y o )
Now that's interesting. I believe I may be tightening them too much, however the leak happens even when the shell is off entirely so I maybe that's not the cause. Thanks for the insight Boobie!

#10 BoobieM4H

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Posted 06 May 2013 - 08:59 PM

View PostGeneral Pickle, on 06 May 2013 - 08:48 PM, said:

Now that's interesting. I believe I may be tightening them too much, however the leak happens even when the shell is off entirely so I maybe that's not the cause. Thanks for the insight Boobie!
If you fix the leak and its out if the shell then its good..just when you insert in shell and tighten the screws..I would tighten until it stops ..then maybe a 1/4 turn more.

( o Y o )



#11 S.Rivard

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Posted 01 August 2013 - 02:04 PM

I use this!

Posted Image

http://www.permatex....et-maker-detail

#12 General Pickle

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Posted 01 August 2013 - 05:10 PM

View PostS.Rivard, on 01 August 2013 - 02:04 PM, said:

Good stuff! I tried a very similar fix but I think I didn't use enough, though I have used it on my MP7 mags with success.

#13 okay47

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Posted 03 August 2013 - 01:37 AM

Yup, I used rtv black and that works fine as well.  Follow akira and boobie's instructions and you should be set.  Clean it thoroughly with alcohol and let it air dry a bit (5 min).  I applied rtv at the base after removing the gasket, then placed the gasket back on and added a little more rtv.  Place the base back onto the mag and screw it back on.  Then add some gas and quickly release it then let it cure overnight (I left mine in the sun).  Once it has cured then you can insert it back inside the shell and lightly tighten (finger tight) the base screws.

EDIT: just thought I needed to clarify why I added gas immediately after applying.  This is so the gas will push the rtv to the areas of the gasket and mag which contain air bubbles and aren't actually sealing your base.  This, IMO, should ensure that you get a better seal from the rtv, just don't add too much gas.  I did a half second push and then immediately released it with the button.  Some don't like to do that since it may ruin your release valve.  I'M CRAZY I DON'T CURR.

On some of my mags that I knew to be very leaky I even added rtv around the outer portion of the base, covering even the pins and screws.  This is because some of the mags actually were leaking through the pins and many of them were leaking through the portion of the base which holds up the spring and bb follower.   I figured if it's going to leak after this then it's going to leak anyway.  They won't be pretty, they're a bit snug to slide back into the pmag shell, and fixing them later on won't be easy but as of right now they hold gas just as well as the STANAG mags.

Good luck

Edited by okay47, 03 August 2013 - 01:57 AM.


#14 BeachEMT

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Posted 12 February 2014 - 01:51 PM

Hey guys, I figured I'd dredge up this old topic to see how this fix is holding up long term. I'm down to only 2 working Pmags out of 6. It feels like as soon as I get one holding gas, 2 more start leaking. I'm getting desperate for a good solution. Thanks!

#15 General Pickle

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Posted 12 February 2014 - 06:53 PM

View PostBeachEMT, on 12 February 2014 - 01:51 PM, said:

Hey guys, I figured I'd dredge up this old topic to see how this fix is holding up long term. I'm down to only 2 working Pmags out of 6. It feels like as soon as I get one holding gas, 2 more start leaking. I'm getting desperate for a good solution. Thanks!
I've used a silicone sealant, made for outdoor and high/low temperature use, very similar to the one pictured above. So far ever since I did the repair I haven't had a single one leak. I successfully completed the repair sometime last year around the end of summer on maybe 5 pmags total and a couple of MP7 magazines, so far they're all just fine. Make sure you use a nice glob of the stuff, and to be safe be sure to wait a full 24 hours before gassing them.

#16 netpoc

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Posted 13 February 2014 - 09:18 AM

I use Frog Lube paste and since having started using it I have not had to repair them (fix leaks). Just use a good coating on it and give it time to swell the o-rings (it may not seal immediately), but once it does, I'm finding you're pretty well set. I was having problems with the silicone drying out and causing the o-rings and gaskets to, what felt like, actually shrink. Once I started using the Frog Lube paste; no more leaks.

#17 BeachEMT

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Posted 13 February 2014 - 01:48 PM

I've been using froglube with no luck, so I think I need something more drastic.

Pickle- I just want to double check on the procedure. 1) Clean parts with alcohol. 2) Apply gasket maker to the base plate and mag body (parts #6 & 7). 3) Assemble the mag back together as normal. 4) Give 24 hours to cure.

#18 netpoc

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Posted 13 February 2014 - 01:55 PM

The paste, or the liquid? The liquid did not work for me either. I had to use the paste and it's working great.

#19 okay47

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Posted 13 February 2014 - 02:23 PM

Hmmm, I should try that.  I have the paste but I haven't been out to play as much.  I've had 2 mags start leaking since I've patched them up but overall they're holding up nicely.  Not sure if I want to remove the RTV and then reapply frog lube paste.  Anyway, good luck Beach.  I'd sell you my mags but I may end up playing again, heh.  Oh and the STANAG mags haven't leaked, ever.

#20 BeachEMT

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Posted 13 February 2014 - 07:02 PM

View Postnetpoc, on 13 February 2014 - 01:55 PM, said:

The paste, or the liquid? The liquid did not work for me either. I had to use the paste and it's working great.
Liquid. What do you guys think, Froglube paste or RTV?





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