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M4A1 firing issues.


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#1 snuff

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Posted 13 February 2013 - 06:29 AM

I've had my M4A1 from new the only addition was a mosfet fitted prior to purchase.
In the 18~24 months that I've had it this only issue,bb's started to roll out of the end,double feed and miss-feed.
I opted for the obvious and changed the hop rubber,3 times in fact,the last time today,on semi it will fire 40-50 bb's then one will roll out of the barrel with what seems to be a stiffled shot as in a blocked barrel,miss a shot then resume feeding.
The more I use it the worse it gets over the course of a day,full auto fires and miss-fires as it chooses.
I have tried 2 brands of bb's(always .25's) and have been using these for 4~6 months,playing at least once a month.

#2 Chuck S

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Posted 13 February 2013 - 03:23 PM

How may shots thru the gun?  The gun will need maintenance at some point and it may be time for yours.  Oil soaked bucking is a common cause of this problem.  I know you've replaced yours previously but what does it look like now?

-- Chuck

#3 philsaudio

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Posted 14 February 2013 - 05:38 AM

Dirty or worn magazines can cause this too.

#4 snuff

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Posted 15 February 2013 - 02:23 AM

View PostChuck S, on 13 February 2013 - 03:23 PM, said:

How may shots thru the gun? The gun will need maintenance at some point and it may be time for yours. Oil soaked bucking is a common cause of this problem. I know you've replaced yours previously but what does it look like now? -- Chuck
I would estimate approx' 40-50,ooo bb's over the time I've owned it.The old bucking didn't look to bad but I opted to change that as I thpought it was the "obvious" issue.
The gearbox is apart now and someone has offered to check it out for me,I didn't notice anything broken but it did seemed a tad gummed up with oil/grease debris.
Everytime I asked about maintenance I was told leave it if it works??The odd spray of silicone is all it got.


View Postphilsaudio, on 14 February 2013 - 05:38 AM, said:

Dirty or worn magazines can cause this too.
They will be my next option,2 are KWA originals,one is a hk copy and one is a brand new ICS.

Thanks to both of you for your advice,I'm waiting to hear back from the tech...

#5 niko_gpsy

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Posted 15 February 2013 - 04:54 AM

View Postsnuff, on 15 February 2013 - 02:23 AM, said:


Everytime I asked about maintenance I was told leave it if it works??The odd spray of silicone is all it got...

You should never use silicone spray in your hop up or magazines.  It will cause your bucking to swell and can lead to jams or misfires.
Are you using silicone every time you change your bucking?

#6 snuff

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Posted 15 February 2013 - 07:04 AM

No only after it became problematic...not used on the latest bucking.

#7 niko_gpsy

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Posted 15 February 2013 - 08:06 AM

Are you using an aftermarket flash hider? Some flash hider opening can be smaller than the outer diameter of the inner barrel thus not allowing free back and forth movement of the hop up which can also lead to your problems.
Once in awhile I get guns like that and after reseating the bb feed ramp and even changing the hop up unit solves any feeding problems.

#8 snuff

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Posted 15 February 2013 - 12:07 PM

View Postniko_gpsy, on 15 February 2013 - 08:06 AM, said:

Are you using an aftermarket flash hider? Some flash hider opening can be smaller than the outer diameter of the inner barrel thus not allowing free back and forth movement of the hop up which can also lead to your problems.
Once in awhile I get guns like that and after reseating the bb feed ramp and even changing the hop up unit solves any feeding problems.
No it's as I've used it since I puirchased it.

#9 gcw360

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Posted 15 February 2013 - 09:25 PM

There are lot's of things that can cause feeding issues.  I will attempt to list the most common:
  • BB's - What ones are you using?

  • Mag - Already mentioned, but bad mags don't feed well

  • Hop-up/bucking interface - covered above but seems to be eliminated?  Double check this...

  • BB feed ramp - If it's not aligned properly, this misfeeding can happen! You may need a new one

  • Wait???You have an M4A1 correct? Where are the MOSFET wires? Are they pushing down on the mag causing a misfeed?  Check to see if this could be happening.  This happened to me about a month ago!


#10 snuff

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Posted 16 February 2013 - 01:48 AM

View Postgcw360, on 15 February 2013 - 09:25 PM, said:

There are lot's of things that can cause feeding issues.  I will attempt to list the most common:
  • BB's - What ones are you using?

  • Mag - Already mentioned, but bad mags don't feed well

  • Hop-up/bucking interface - covered above but seems to be eliminated?  Double check this...

  • BB feed ramp - If it's not aligned properly, this misfeeding can happen! You may need a new one

  • Wait???You have an M4A1 correct? Where are the MOSFET wires? Are they pushing down on the mag causing a misfeed?  Check to see if this could be happening.  This happened to me about a month ago!

Number 5 did occur to me but I pushed them high up with a flat-blade screwdriver,the wires do tend to run across the mag interface.
I have to ask why would this issue suddenly happen?I'm looking for a change somewhere..
I will get to the bottom of it,it is now in the hands of an expert....

#11 gcw360

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Posted 16 February 2013 - 07:21 AM

View Postsnuff, on 16 February 2013 - 01:48 AM, said:


Number 5 did occur to me but I pushed them high up with a flat-blade screwdriver,the wires do tend to run across the mag interface.
I have to ask why would this issue suddenly happen?I'm looking for a change somewhere..
I will get to the bottom of it,it is now in the hands of an expert....
If you crack open the gun to clean the barrel, and the gun is front wired like the M4A1, the wires can tighten and move as you open the gun.  The can then push down on the mag.  This is why I suggested #5.  It could also account for the fact that it's a new occurrence.

Let us know what the outcome is.

#12 snuff

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Posted 16 February 2013 - 08:55 AM

View Postgcw360, on 16 February 2013 - 07:21 AM, said:

If you crack open the gun to clean the barrel, and the gun is front wired like the M4A1, the wires can tighten and move as you open the gun.  The can then push down on the mag.  This is why I suggested #5.  It could also account for the fact that it's a new occurrence.

Let us know what the outcome is.
I appreciate that and I will bear that in mind although I was aware of it anyway.
What I'm saying is the issue occured prior to me opening the gun up,it is something else to be ruled out.
I'm waiting for the expert to contact me,I now there was a delivery failure today so he'll get it monday.
I will let you know the out come,thanks.

#13 snuff

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Posted 19 February 2013 - 10:41 AM

I spoke to another long term owner today,he suffered the same issue and he discovered that his mag catch was worn allowing the mag to drop slightly,leading to the same issues I'm experiencing.
The tech's have it now so I'm waiting to hear...

#14 gcw360

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Posted 19 February 2013 - 06:42 PM

View Postsnuff, on 19 February 2013 - 10:41 AM, said:

I spoke to another long term owner today,he suffered the same issue and he discovered that his mag catch was worn allowing the mag to drop slightly,leading to the same issues I'm experiencing.
The tech's have it now so I'm waiting to hear...
Sorry I didn't think of that.  I have seen it too.  In fact, one time all that was needed was the mag release screw to be tightened and problem solved.  I hope it's something so simple.  Please keep us posted.

#15 snuff

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Posted 13 April 2013 - 11:54 AM

Paid the tech's to sort it,they replaced worn out parts but the issue still prvails.
I've "borrowed" the mag release catch from my m8's KWA,it seems to be a firmer engagement, I'll see how it goes on 21/04...cheers for all the advice.

#16 gcw360

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Posted 13 April 2013 - 08:27 PM

Please keep us posted.

#17 snuff

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Posted 21 April 2013 - 11:00 AM

No joy..fired perfectly for about 10 mags (1500~2000 bbs) then the issue reappeared.
Double feeding,not feeding,bb's rolling out of the end,I'm at my wits end with this..any help welcomed.
I took it into the site shop and they had a look,they said that with the hop completely off it worked ok,as soon as the hop was applied it went wrong,they suggested the hop rubber,I'll try but I've swapped it out 3 times,this time it will be a genuine KWA hop rubber.
Why is it starting so well then going to pot?It didn't ruin my day but it may do soon...thanks..

#18 gcw360

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Posted 21 April 2013 - 03:17 PM

View Postsnuff, on 21 April 2013 - 11:00 AM, said:

No joy..fired perfectly for about 10 mags (1500~2000 bbs) then the issue reappeared.
Double feeding,not feeding,bb's rolling out of the end,I'm at my wits end with this..any help welcomed.
I took it into the site shop and they had a look,they said that with the hop completely off it worked ok,as soon as the hop was applied it went wrong,they suggested the hop rubber,I'll try but I've swapped it out 3 times,this time it will be a genuine KWA hop rubber.
Why is it starting so well then going to pot?It didn't ruin my day but it may do soon...thanks..
What rubber have you been using thus far?

#19 TicTac

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Posted 21 April 2013 - 03:29 PM

its a tappet plate lol

#20 gcw360

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Posted 21 April 2013 - 04:57 PM

View PostTicTac, on 21 April 2013 - 03:29 PM, said:

its a tappet plate lol
What?




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