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Bolt Catch Not Working

lm4 bolt catch

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#1 FlubberDucky

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Posted 02 January 2013 - 10:28 PM

So after ~5000 rounds put into my lm4 that hasnt failed me once, the bolt catch has stopped working. Its not the bolt cause i put in my friends brand new bolt that is perfect and squared and it still didnt work. The problem seems to be that the bolt catch isnt actually going up to engage the bolt, it just doesnt get pushed up to engage it at all, and no its not the mags. Ive taken the bolt catch apart and ive put more tension on the detent spring thing thats in there, but everything seems to be fine. The bolt catch is also very soft and takes little force to release the bolt. What is the problem? Should i send in the entire rifle to kwa and have them take care of it? (i really dont wanna do that) Or should i just call the pro shop and have them send me a new bolt catch / whole new firing pin block thing? What should I do? Please help me and respond, nobody seems to respond to anything i ever post :cry:

#2 ATOMANT

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Posted 03 January 2013 - 06:59 AM

If the part is not expensive, then just buy it all. It will probably get replaced by the tech any ways. You gotta start somewhere. I looked at how it all works on my gun and if the bolt didnt fix it, then your on the right trrack replacing the other associated parts. Plus the money you save not involving a tech will pay for the testing pieces.

#3 Chuck S

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Posted 03 January 2013 - 07:02 AM

The stock LM4 bolt catch detent and spring hold the bolt catch OFF or ON.  There's two little dimples in the bolt catch.

Increasing spring pressure will tend to hold it OFF more tightly, exactly opposite what you want.  Too little spring pressure, though, will allow the bolt catch to bounce ON when you least expect it.  The bolt catch is activated by the magazine follower and a weak follower will not push hard enough.

The simple modification to the bolt catch to allow it to function like the real M4 will solve this problem.  Just follow the instructions patiently.  Even I was able to do it!  :)  There's a tab on the front of the magazine catch that can be reformed (never bent!) to raise the it higher.  This is covered in the modification instructions but can be applied separately.

Note:  Slapping the bolt catch to close the bolt looks tactikool but causes wear on the catch and bolt carrier in these guns unlike their 5.56mm sisters.

-- Chuck

Edited by Chuck S, 03 January 2013 - 07:05 AM.


#4 shaofengli

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Posted 04 January 2013 - 10:46 AM

View PostChuck S, on 03 January 2013 - 07:02 AM, said:

The stock LM4 bolt catch detent and spring hold the bolt catch OFF or ON.  There's two little dimples in the bolt catch.

Increasing spring pressure will tend to hold it OFF more tightly, exactly opposite what you want.  Too little spring pressure, though, will allow the bolt catch to bounce ON when you least expect it.  The bolt catch is activated by the magazine follower and a weak follower will not push hard enough.

The simple modification to the bolt catch to allow it to function like the real M4 will solve this problem.  Just follow the instructions patiently.  Even I was able to do it!  :)  There's a tab on the front of the magazine catch that can be reformed (never bent!) to raise the it higher.  This is covered in the modification instructions but can be applied separately.

Note:  Slapping the bolt catch to close the bolt looks tactikool but causes wear on the catch and bolt carrier in these guns unlike their 5.56mm sisters.

-- Chuck
hey chuck, how do u reform the tab.  i watched Akira's bolt catch mod. the tab needs to be bent. are we talking about the same thing? can u post a picture of it? thanks

Edited by shaofengli, 04 January 2013 - 03:15 PM.


#5 Raptor72

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Posted 04 January 2013 - 11:20 AM

I most definitely bent mine.  That was like 6 months ago.  I havent looked back.

#6 Outlaw1995

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Posted 04 January 2013 - 11:49 AM

It is the arm that hangs over the magazine well, and gets pushed up by the bolt stop system in the magazine. Part 16 on this diagram:

http://kwausa.com/fi..._B02_LM4PTR.jpg

#7 akiraspeedstar

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Posted 04 January 2013 - 01:52 PM

Another option other than ending it would be to add some epoxy to the bottom and shave it to the correct height. You could also add some heat shrink wire wrap to add some mass to the area as well. I found that bending the arm was a very easy process and didnt run the risk of anything falling off and jamming the internals.

I haven't had an issue as of yet with the bolt stop since completing this modification. I've taken apart the impact block and everything is holding up as it should.

#8 FlubberDucky

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Posted 04 January 2013 - 06:55 PM

Ok well i took apart the bolt catch and i compressed the detent spring in there and played around with some stuff to see if I could get it to work and when I put everything back together it magically worked again! Yep the bolt catch is now catching the bolt somehow, but its still a really soft push to make it send the bolt home. I really have no idea why its so easy to push down, even shaking the rifle around makes it send the bolt home. I dont think it would be the bolt face that needs shaving, but it could be the problem. I just dont know what a rounded bcg looks like cause it doesnt seem very rounded on mine.

#9 gcw360

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Posted 04 January 2013 - 07:56 PM

View PostFlubberDucky, on 04 January 2013 - 06:55 PM, said:

Ok well i took apart the bolt catch and i compressed the detent spring in there and played around with some stuff to see if I could get it to work and when I put everything back together it magically worked again! Yep the bolt catch is now catching the bolt somehow, but its still a really soft push to make it send the bolt home. I really have no idea why its so easy to push down, even shaking the rifle around makes it send the bolt home. I dont think it would be the bolt face that needs shaving, but it could be the problem. I just dont know what a rounded bcg looks like cause it doesnt seem very rounded on mine.
If you follow Akira's video, you shouldn't have a bolt catch issue any longer.  I did the mod, and it works like a dream.

Behold...a slightly "rounded bolt" : <a href="http://s814.beta.pho..._2865.jpg.html" target="_blank"><img src="http://i814.photobuc...0/IMG_2865.jpg" border="0" alt="Photobucket"/></a>

Look at the top left of the end of the bolt...note: The bolt is upside down facing left....

#10 FlubberDucky

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Posted 04 January 2013 - 09:57 PM

View Postgcw360, on 04 January 2013 - 07:56 PM, said:

If you follow Akira's video, you shouldn't have a bolt catch issue any longer.  I did the mod, and it works like a dream.

Behold...a slightly "rounded bolt" : <a href="http://s814.beta.pho..._2865.jpg.html" target="_blank"><img src="http://i814.photobuc...0/IMG_2865.jpg" border="0" alt="Photobucket"/></a>

Look at the top left of the end of the bolt...note: The bolt is upside down facing left....
Thanks! Now I know what a rounded bolt really looks like :P but mine is no where near that...Compared to that it actually looks like mine is perfectly new. Im still unsure if my bolt is rounded or not. If it is, how do i go about fixing it?

#11 Chuck S

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Posted 05 January 2013 - 06:45 AM

Amateurs bend stuff.  Professionals reform it.  :)

-- Chuck

#12 gcw360

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Posted 05 January 2013 - 08:32 AM

View PostFlubberDucky, on 04 January 2013 - 09:57 PM, said:

Thanks! Now I know what a rounded bolt really looks like :P but mine is no where near that...Compared to that it actually looks like mine is perfectly new. Im still unsure if my bolt is rounded or not. If it is, how do i go about fixing it?
After you do the bolt mod, simply file the face flat.





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