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LM4 Upper Receiver Rail Loose

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#1 FlubberDucky

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Posted 11 August 2012 - 10:12 AM

Well today I noticed that the rail on the upper receiver is sort of separated into 3 parts. Theres the actual upper, then some piece in between for the charging handle i suppose, and then the rail which seems to be sort of glued on to the top. I use a sort of an acog looking tactical scope on it and its a bit heavy and today i noticed that it was starting to wobble. I looked a bit closer and the rail part on the top is a bit loose causing my optics to wobble around. I don't know what the problem is and i really want to fix it because i hate my wobbly optics. Anyone know of a way to fix this?

#2 jonsun81

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Posted 11 August 2012 - 10:18 AM

The upper assembly is in fact three pieces, the upper itself is two peices with the rail pinned on.  what you can do is use a ras fix, from your rail to upper receiver and thatll hold it steady.  some people even attach their red dots this way but may not work for your acog, too far from your eye.

#3 Jatodude

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Posted 11 August 2012 - 04:32 PM

This is a problem that has already been addressed quite a few times. There's already a topic in the LM4 sub-forums about this too. But anyways, here's the fix: http://kwausa.com/fo...?showtopic=1798
I've done this twice now, once for the SR-12, and secondly for the LM4. It's the same process. I've always used just regular paper as a shim. It's worked perfectly.

#4 akiraspeedstar

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Posted 11 August 2012 - 04:47 PM

I used a very thin piece of plastic which was actually the plastic packaging for some tools. The wobble is unfortunately still there, though it's extremely minor.

#5 FlubberDucky

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Posted 11 August 2012 - 06:38 PM

View PostJatodude, on 11 August 2012 - 04:32 PM, said:

This is a problem that has already been addressed quite a few times. There's already a topic in the LM4 sub-forums about this too. But anyways, here's the fix: http://kwausa.com/fo...?showtopic=1798
I've done this twice now, once for the SR-12, and secondly for the LM4. It's the same process. I've always used just regular paper as a shim. It's worked perfectly.
is there any way i can do this without having to completely remove the hop up and barrel since im a newbie at that stuff?

#6 akiraspeedstar

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Posted 11 August 2012 - 07:37 PM

You don't have to remove the hopup or barrel, just tap out the pin, remove the rail, place the shim, and replace the rail, and tap the pin back in. It takes less then 5 minutes from start to finish, longer if you're needing to find the right shim size or thickness.

#7 FlubberDucky

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Posted 11 August 2012 - 08:07 PM

View Postakiraspeedstar, on 11 August 2012 - 07:37 PM, said:

You don't have to remove the hopup or barrel, just tap out the pin, remove the rail, place the shim, and replace the rail, and tap the pin back in. It takes less then 5 minutes from start to finish, longer if you're needing to find the right shim size or thickness.
Thanks for the info brother! I guess ill be looking into this tomorrow and it should be ready by monday. Thanks!





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