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After adding rail to LM4, only getting 10 shots per mag. Any ideas?

LM4 green gas magazine

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#1 Joel Bonnette

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Posted 18 November 2013 - 10:21 PM

Hi Guys, I'm just getting into airsoft and have very little experience.  I'm having an issue with my new LM4 PTR that I recently picked up. I ran 3 mags through it and it was functioning well.  I got through 2/2.5 mag bb reloads before having to add green gas.  I put it away (without cleaning).  It sat for a week and I pulled it out last night to add a rail.  After adding the rail, I shot it again and now I am getting about 10 shots before the mag is completely empty of all gas.  I only have 1 magazine currently. I've added gas from three different green gas cans and fill for about 30-40 seconds.  Any idea on what the issue might be? What damage might I have done?

Thanks! Joel

#2 BeachEMT

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Posted 18 November 2013 - 11:08 PM

Hi Joel. Welcome to the forums!

I highly doubt a rail is the cause of your issues. Even still, what type of rail is it? Did you have to change the barrel nut?

Do you live in a colder climate? Has the temperature dropped significantly in the last week? This would be my first guess knowing nothing else.

Lastly, you didn't happen to hear any hissing or other sounds associated with a gas leak, did you? LM4 magazines are notorious for leaking, especially from the factory. I'm currently only 3/6 on working mags and at one point I was 1/6.

#3 Joel Bonnette

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Posted 19 November 2013 - 12:31 AM

Thanks Beach, I appreciate the welcome and the quick response!  After a bit more research, I figured out the culprit.  I was not filling my mag up side down.  Did I mention that I am a newb? Lol.  After filling the mag correctly, I was able to get back to the 2-3 mags per refill.

I ended up adding a RS Heads Down Provectus 13" rail. Had to do some small mods but it ended up fitting pretty well.  Getting the stock barrel nut off was a huge pain.  I had to use a lot of force to get it off and felt that I might have damaged something in the process.  Glad to know that I didn't now :). I uploaded a pic of it.  It's still a work in progress but I'm liking how it looks.

Thanks again!

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#4 Elx3248

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Posted 19 November 2013 - 01:33 AM

hey joel how did you rethread the upper? i used the barrel nut to rethread one of my uppers but man was it a pain.

#5 Joel Bonnette

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Posted 19 November 2013 - 08:37 AM

View PostElx3248, on 19 November 2013 - 01:33 AM, said:

hey joel how did you rethread the upper? i used the barrel nut to rethread one of my uppers but man was it a pain.

The new barrel nut would go on about 1/2 way.  At that point it would get too tight to go any further.  I found this article that discussed someone having a simiar issue: http://airsoft-guns-...4-ptr-gbbr.html
So I tried that method using a dremel wire brush to clean out the threads on the upper and the new barrel nut.  After cleaning up the threads, I was able to get the barrel nut more than 3/4.  At that point I was able to use an extra 2mm shim to get the barrel properly secured in place. The rail also had some indexing tabs that I had to file down just a bit.  All in all, I'm happy with the final product. :)





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