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Full-auto trouble shooting


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#1 Jatodude

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Posted 08 June 2012 - 10:33 AM

Well like the title says, my LM4 is behaving strangely in full auto.  In semi auto I can blast through a whole mag as fast as I can with no problems.  But in full auto I started noticing bb's dropping occasionally and more recently it skips a shot leading to expulsion of gas and then goes back to normal on the next shot.  I can fire short bursts in full auto, but after about 5 shots the bb's start decreasing in speed and eventually it misfires.  I'm guessing it has something to do with the piston inside the bolt not behaving correctly.  I think it's ejecting from the hop-up chamber too early.  Maybe the cool down is causing the seal to become weaker?

Edited by Jatodude, 08 June 2012 - 10:34 AM.


#2 niko_gpsy

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Posted 08 June 2012 - 12:44 PM

Possible.......................... you might also want to check the release valve and bb follower spring in the mag.  Are you seeing excessive wear on the cylinder especially the little metal part that loads the bb?
And also try adding a drop of silicone oil in the cylinder to see if that helps.
Have you made any modifications to the gun yet?

#3 Jatodude

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Posted 08 June 2012 - 02:59 PM

Well I have two mags, and only one works.  The other one started leaking within a day and I haven't gotten around to sending it back.  I replaced the top part of the working magazine with the broken one so it had basically no wear on it. Same thing happened.  Although it did seem to work a little bit better.  I don't see any excess wear anywhere either.

#4 Cariza

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Posted 08 June 2012 - 07:36 PM

I'm experiencing the same full auto problems. I will clean the gun and lube it to see if it helps. Mine starting doing it when I changed green gas brands. I'm using a 11kg of pressure bottle when before it was a 9 kg. Maybe that's the culprit.

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#5 BoobieM4H

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Posted 08 June 2012 - 08:49 PM

Change the oring on the loading nozzle to a slightly larger diameter..and I mean slightly larger. I think you're losing compression. I was experiencing the same issues with mine until I changed the oring. I used a 35/64" x 23/32" x 3/32" hnbr (hydrogenated nitrile butadiene rubber) oring..bought an oring kit actually from harbor freight with a bunch of different sizes.

#6 Jatodude

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Posted 09 June 2012 - 08:23 PM

View PostBoobieM4H, on 08 June 2012 - 08:49 PM, said:

Change the oring on the loading nozzle to a slightly larger diameter..and I mean slightly larger. I think you're losing compression. I was experiencing the same issues with mine until I changed the oring. I used a 35/64" x 23/32" x 3/32" hnbr (hydrogenated nitrile butadiene rubber) oring..bought an oring kit actually from harbor freight with a bunch of different sizes.
Thanks for the advice.  I'll be sure to try that out.

#7 niko_gpsy

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Posted 12 June 2012 - 04:48 AM

I just noticed on my LM4 was dropping bb's too.  I turned the hopup down by a click or so and no more problem.  The hopup I have found is very sensitive to adjustments and too much will cause a slight jamming effect causing the bb's to drop in full auto.

#8 Jatodude

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Posted 12 June 2012 - 09:22 AM

View Postniko_gpsy, on 12 June 2012 - 04:48 AM, said:

I just noticed on my LM4 was dropping bb's too.  I turned the hopup down by a click or so and no more problem.  The hopup I have found is very sensitive to adjustments and too much will cause a slight jamming effect causing the bb's to drop in full auto.
I tried messing with that.  From all the way up, to all the way down.  No effect.  I'm going to try and replace the O-Ring like BoobieM4H said.




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