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Full auto problems

Full auto piston O-ring O-ring O ring Piston O ring wat do?

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#1 Rivalevanator

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Posted 31 August 2013 - 03:59 PM

I've been having problems on full auto for quite awhile now on my LM4.  I mostly looked past it, as I generally only use semi-auto.  However, a couple days ago I decided to tackle the issue, and look for a solution.  Mostly everyone said to replace the piston O-ring for better compression.  I did just that.  Even though the compression is far better than before, I still have issues in full auto.



Here is a short video I took of it, it's not the best, but you can see the bbs dropping instead of going towards the target (the cardboard)

#2 gcw360

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Posted 31 August 2013 - 06:31 PM

View PostRivalevanator, on 31 August 2013 - 03:59 PM, said:

I've been having problems on full auto for quite awhile now on my LM4.  I mostly looked past it, as I generally only use semi-auto.  However, a couple days ago I decided to tackle the issue, and look for a solution.  Mostly everyone said to replace the piston O-ring for better compression.  I did just that.  Even though the compression is far better than before, I still have issues in full auto.



Here is a short video I took of it, it's not the best, but you can see the bbs dropping instead of going towards the target (the cardboard)
With all due respect, what exactly is the issue?  Maybe it's just me but I can't tell what's wrong based on the video you posted.  Would you describe it please?

#3 Rivalevanator

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Posted 31 August 2013 - 10:30 PM

View Postgcw360, on 31 August 2013 - 06:31 PM, said:

With all due respect, what exactly is the issue?  Maybe it's just me but I can't tell what's wrong based on the video you posted.  Would you describe it please?

Yeah, the video wasn't great.  I just wanted to film something fast and get out of the heat.  Anyway, everything functions fine on semi-auto.  However, when I swap over to full auto, I get some major consistency issues.  The shots will either fly everywhere like they've been shot out of a scattergun, curve down really hard (you can kinda see that in the video), or just roll out of the barrel.

Edited by Rivalevanator, 31 August 2013 - 10:31 PM.


#4 Chuck S

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Posted 01 September 2013 - 02:14 AM

I had a similar problem when my LM4 was new.  I occasionally had BBs roll out of the barrel and others fall far short of the target.

Since my gun was under warranty (and still had the orange tip) KWA fixed it promptly under warranty.  Send it to them even if it's out of warranty.  No problems is a year.  KWA replaced the hopup and did some work on the bolt.

-- Chuck

#5 Rivalevanator

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Posted 01 September 2013 - 05:38 PM

K, it's not as hot today so I reshot the video.



You can really see the bbs drop when I go to full auto now.  Also, I though the gun stopped shooting because I was out off bbs.

http://i.imgur.com/mWg3zjc.jpg

Guess, not.  This happens only on full auto.

What do I need to buy/fix/replace to stop this from happening?

Edited by Rivalevanator, 01 September 2013 - 05:41 PM.


#6 Chuck S

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Posted 02 September 2013 - 03:45 AM

More of the exact problem I had with my LM4 a year ago.  A quick trip to KWA fixed it nicely.  My guess is it was an oil soaked bucking and other hopup issues.

Amateur disassembly of the LM4 to get to the bucking is fraught with the possibility of breaking the upper receiver.  There are detailed instructions on how to do this elsewhere on the forum but impatience will still bust the gun.

Still strongly recommend sending the gun to KWA.  Mine works wonderfully since it's trip and is shooting 3" groups at 25 meters -- pretty good for a stock airsoft gun.

-- Chuck

#7 Nitemare

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Posted 02 September 2013 - 06:36 AM

I disagree. Taking apart the upper is not very difficult. An armorer's wrench. hair drier to heat up the barrel nut, and tact approach will work nicely. The knowledge and tools of taking apart the weapon are invaluable when it comes to not only diagnosing and fixing issues, but installing upgraded parts.

I would give the barrel a good clean first with the rod and cleaning patches soaked in silicon oil, then run dry patches through. Then, proceed to use a few q-tips to clean the bucking by taking apart the receivers. You can easily reach the main parts without disassembling the hop assembly. Soak the ends in soapy water and wipe down the bucking gently. Then hit it with a q-tip soaked in only water. Dry it gently, and see if it comes out dirty still.

Past this, good lubrication is helpful. If you can, lubricate all around the piston, and a generous layer inside of the bolt where the piston travels. Make sure the piston o-ring is not dry either (hopefully you lubed it all around when you fit it on). These simple steps should alleviate the issue, or show that it is a bigger issue.

Also, what o-ring did you replace it with? I tried the Danco, but got less than desirable results (individually packed ones). It seemed like too big of a fit. The Harbor Freight kit rings seem almost too small, but work fine, and this is where the lubrication helps with the seal as well.

Edited by Nitemare, 02 September 2013 - 06:44 AM.


#8 General Pickle

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Posted 02 September 2013 - 11:02 AM

What I have found is that the stock bucking is simply not capable of holding the BB's in place 50% of the time. I had these same issues with my LM4 and sometimes if I was just standing around with my gun pointed down the BB's would roll out the barrel. I determined it could only be due to a faulty bucking. After I replaced the bucking with the Maple Leaf and EVO II hop-up set, both of these issues have never resurfaced.

As for the double feeding, full auto will definitely cause that more than semi-auto will. There's a known fix for this problem, of which I was a little skeptical at first but after I did the mod it has proved to prevent doubles feeds since then.

http://www.kwausa.co...pic=11372&st=40

https://www.youtube....be_gdata_player

I used the o-ring method, which it does seem to dislodge after so much recoil and cleaning but after I realized this I cut the groove deeper and haven't had issues since then. This is of course if you're comfortable with doing tech work on your own guns. If you're not confident in your tech skills your best option is to send it to KWA or if there's a local tech you trust then he/she could probably do it.

#9 Rivalevanator

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Posted 02 September 2013 - 03:55 PM

Nitemare,
I used this O-ring
http://i.imgur.com/hInl9c9.jpg
These were at home depot, they're the same dimensions as the danco
http://i.imgur.com/y9a7DCG.png

General Pickle, so the problem is my hop up?  My dad has a Evo II for his Kriss that he's not using.  If I put that on my gun, then I won't get all the inconsistency on full auto?

Edited by Rivalevanator, 03 September 2013 - 02:29 PM.


#10 General Pickle

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Posted 03 September 2013 - 01:01 AM

View PostRivalevanator, on 02 September 2013 - 03:55 PM, said:

Nitemare,
I used this O-ring
http://i.imgur.com/hInl9c9.jpg
These were at home depot, they're the same dimensions as the danco
http://i.imgur.com/y9a7DCG.png

General Pickle, so the problem is my hop up?  My dad has a Evo II for his Kriss that he's not using.  If I put that on my can, then I won't get all the inconsistency on full auto?
From my experience, yes. I found that the EVO II set stopped the BB's from rolling out the barrel and generally improved the consistency. Keep in mind though that without the 'o-ring and barrel' mod you may not get the consistency you want, plus the double feeds will likely still occur. I have not installed a tight bore yet, so I would imagine that doing that would increase the consistency even more.





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