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CQR mod 1 eratic firing on full auto


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#1 hellcat

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Posted 24 January 2014 - 02:29 PM

Need some help guys. Working on a friends gun.  When shooting on full auto I'm getting a lot of dribbler shots....5,6 bb's will go out to full range and then 2,3 will only go 30 ft..  All bb's shoot properly on semi.  I had this same problem on my SR7 and I was able to correct by replacing the cylinder with one from SR-10

Gun is all stock.
11.1 lipo
.30g madbull bb's
KWA 120 mid caps.

Bucking and hop up have been cleaned and inspected.
Gear box has been opened up, cleaned and inspected. Danco#14 o-ring added to piston head.
Tried multiple mags. fully loaded and half loaded..I don't think it is a feed issue.
I tried to use a 7.4 lipo and got the same results.

Thanks guys

Edited by hellcat, 28 January 2014 - 04:40 PM.


#2 iWar

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Posted 24 January 2014 - 03:16 PM

Sounds like a tappet plate issue, or maybe the sector clip... Seems like your not getting a full air seal on full auto...

Edited by iWar, 25 January 2014 - 06:56 AM.


#3 gcw360

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Posted 25 January 2014 - 09:30 AM

View Posthellcat, on 24 January 2014 - 02:29 PM, said:

Need some help guys. Working on a friends gun.  When shooting on full auto I'm getting a lot of dribbler shots....5,6 bb's will go out to full range and then 2,3 will only go 30 ft..  All bb's shoot properly on semi.  I had this same problem on my SR7 and I was able to correct by replacing the cylinder with one from SR-10

Gun is all stock.
11.1 lipo
.30g madbull bb's
KWA 120 mid caps.

Bucking and hop up have been cleaned and inspected.
Gear box has been opened up, cleaned and inspected. Danco#14 o-ring added to piston head.
Tried multiple mags. fully loaded and half loaded..I don't think it is a fee issue.
I tried to use a 7.4 lipo and got the same results.

Thanks guys
Are all the mags tested K-mags?

#4 hellcat

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Posted 25 January 2014 - 11:18 AM

yes they are all K-mags.

This has me really stumped.  Took the gear box apart again this morning...inspected every part, no visible signs of any wear. I even shortened tappet plate spring.
I agree that this a compression problem, I just can't find the issue.

#5 gcw360

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Posted 25 January 2014 - 06:02 PM

View Posthellcat, on 25 January 2014 - 11:18 AM, said:

yes they are all K-mags.

This has me really stumped.  Took the gear box apart again this morning...inspected every part, no visible signs of any wear. I even shortened tappet plate spring.
I agree that this a compression problem, I just can't find the issue.
Actually., I think it's a K-mag issue. That said, it could be a feed ramp issue. A few more questions:
  • How long has this been going on and have yo modified the mags with ranger plates?
  • Did the gun ever not do this?
  • Does it do this on semi and full auto or only F/A?


#6 hellcat

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Posted 26 January 2014 - 12:39 PM

I questioned my friend today,

How long has this been going on ...... as long as he owned the gun.  Just about a year now.
have yo modified the mags with ranger plates......he does not use Ranger plates, he has 12 k-mags.
Did the gun ever not do this?  No.
Does it do this on semi and full auto or only F/A? Only on Full Auto......Shoots perfect on Semi, very coincident.

#7 gcw360

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Posted 26 January 2014 - 04:45 PM

View Posthellcat, on 26 January 2014 - 12:39 PM, said:

I questioned my friend today,

How long has this been going on ...... as long as he owned the gun.  Just about a year now.
have yo modified the mags with ranger plates......he does not use Ranger plates, he has 12 k-mags.
Did the gun ever not do this?  No.
Does it do this on semi and full auto or only F/A? Only on Full Auto......Shoots perfect on Semi, very coincident.
My guest is:
  • Feed ramp not properly seated (maybe)

  • Feed ramp Has a bit of plastic flash from the mold during manufacturing.  This happened for a while with the CQRs.  Look to see if the hole (top and bottom) of the feed ramp needs to be cleaned up with an Exacto knife.  That will probably fix it.

  • Some K-mags have feeding issues that are easily fixed.  Before yo go modding them though do you have another brand of mag you can try?


#8 Rain Man

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Posted 28 January 2014 - 04:49 AM

Is there any possibility you could test it with another brand of magazine? That might at least be able to tell you if its the K mags or not.

#9 hellcat

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Posted 28 January 2014 - 04:34 PM

Feed ramp is clear of any flashing and is properly seated.
I own 14 K-mags. and have tried multiple mags.

I will try a high cap mag. tomorrow after work.

I believe this is a compression issue at the nozzle/hop up unit. Installed new nozzle today, no change in performance.

One thing that I have noticed is that the inner barrel is a little snug in the outer barrel at the point of attachment to the upper body, as compared to my own KM4-RIS and SR-7. Barrel/Hop up will spring back when pushed in with my finger.  What is considered too tight?

I'm also going to install my barrel/hop up from my KM4-RIS and see what happens.

Will report back tomorrow.
If you guys think of anything else let me know.

#10 hellcat

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Posted 29 January 2014 - 03:34 PM

First thing I did today was install my own barrel/hop up unit from my KM4-RIS, then tried a High cap. ICS mag I have. Test fire gun on full Auto......Works perfect, :drooling:. Load up a couple K-Mags and again test fire....Works perfect again. :clap:Pull out my bucket of spare parts and dig out a used bucking and hop unit, Install on original barrel and install in gun. Test fire with K-Mags....Works perfect again. :clap: So problem turns out to be the bucking or hop up unit. There is no visible signs of defects with the original parts that can be seen.

#11 gcw360

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Posted 29 January 2014 - 03:36 PM

View Posthellcat, on 29 January 2014 - 03:34 PM, said:

First thing I did today was install my own barrel/hop up unit from my KM4-RIS, then tried a High cap. ICS mag I have. Test fire gun on full Auto......Works perfect, :drooling:. Load up a couple K-Mags and again test fire....Works perfect again. :clap:Pull out my bucket of spare parts and dig out a used bucking and hop unit, Install on original barrel and install in gun. Test fire with K-Mags....Works perfect again. :clap: So problem turns out to be the bucking or hop up unit. There is no visible signs of defects with the original parts that can be seen.
Is the inner barrel springing back into position now?

#12 hellcat

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Posted 29 January 2014 - 05:10 PM

The barrel did spring back, but it was stiffer then my RIS and SR7. Before I reinstalled the original CQR brass barrel I cleaned up the outside with some maroon scotch brite pad. Does feel ever so slightly smoother as it slides into the outer barrel.

#13 gcw360

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Posted 30 January 2014 - 07:09 AM

View Posthellcat, on 29 January 2014 - 05:10 PM, said:

The barrel did spring back, but it was stiffer then my RIS and SR7. Before I reinstalled the original CQR brass barrel I cleaned up the outside with some maroon scotch brite pad. Does feel ever so slightly smoother as it slides into the outer barrel.
That might have helped significantly.




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