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Jams and Hop Up issues.


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#1 ky2970

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Posted 22 December 2012 - 07:51 PM

Took my LM4 to a game today and I experienced lots of jams and hop up issues. Let's first address the jams. I am not blaming KWA. I have modified my weapon so I do suspect that that is the main cause. First possible cause of increased jamming: modified bolt carrier group. I suspect this may have increased the cycling rate and caused the BBs to double feed. Or could it be: chopped buffer. I had to cut it for the UBR stock. Only the rubber tip was removed. If you know the LM4 through and through, I would really appreciated some insight on this. I plan on buying an entirely new bolt carrier group and bolt that I will keep bone stock.

I notice a LOT more jams with either of my PMAGS.

Hop-up issues. Seems that most owners have problems with their hop-up. I, unfortunately, am plagued with this. The accuracy is all over the place and the hop up is inconsistent. Sometimes the BBs (.30g) will fly perfect and other times they will drop to the deck. The side to side margin of accuracy is rather thin so it proves to definitely be a hop up problem. Please help me.

The final straw for me happened during a game today. I got a double feed and when that happens and you pull the trigger without noticing, it spews gas everywhere. I was trapped by myself behind a pile of rocks. I couldn't just switch mags obviously so I was trapped with just my USP. After the game, I cleared the jam and noticed that the hop up bucking had ripped (pics inbound).

I absolutely love the LM4 but with all these issues, my AEG is looking very very lucrative again... I just want to make it fully function and be as reliable as my AEGs.

#2 Chuck S

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Posted 23 December 2012 - 07:10 AM

You really don't have issues with the LM4.  You have issues to your modifications to it! :)

What did you do to the bolt carrier group?  This is the heart of the gun along with the magazines.

I'd return the gun to stock specifications with a new bolt carrier group, lower receiver extension (get rid of the UBR stock, it just adds weight), and buffer.  But if you're going thru all this trouble send the gun to KWA and let them do it -- and fix your hop up issues as well.  Yeah, this will be an expensive lesson.

-- Chuck

-- Chuck

#3 gcw360

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Posted 23 December 2012 - 08:46 AM

View PostChuck S, on 23 December 2012 - 07:10 AM, said:

You really don't have issues with the LM4.  You have issues to your modifications to it! :)

What did you do to the bolt carrier group?  This is the heart of the gun along with the magazines.

I'd return the gun to stock specifications with a new bolt carrier group, lower receiver extension (get rid of the UBR stock, it just adds weight), and buffer.  But if you're going thru all this trouble send the gun to KWA and let them do it -- and fix your hop up issues as well.  Yeah, this will be an expensive lesson.

-- Chuck

-- Chuck
I agree with Chuck.  There are multiple issues with your gun that can be caused by various problems.  It's at a level of complication that would seem a real challenge to solve here on the Forums without having the gun in hand.

#4 ky2970

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Posted 23 December 2012 - 12:55 PM

Actually I think I've found the source of the issue... I found out that the screws that connect the outer barrel and inner barrel were very very loose. It barely took any force to unscrew them when I disassembled my rifle last night. Do you guys think this could be the source of the jamming? I read somewhere that this causes lots of jams.

Using my friends LM4 BCG I'll test it out and figure out what exactly is causing my malfunctions.

Edited by ky2970, 23 December 2012 - 12:56 PM.


#5 ky2970

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Posted 24 December 2012 - 07:45 PM

Found out the problem... It seems to be with the bolt carrier. Tried my friend's bolt carrier and it worked flawlessly.

#6 that guy with the m4

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Posted 30 December 2012 - 11:26 PM

I think it may be part 2 aka the piston the part that pushes the bbs maybe worn down in a place that is making it jam or i think i was told it could be the movement of the piston. I to have this issue and i love my lm4 and would never pick up an aeg again if i did not have these issues. Can you post pics of the the bb pusher arm. I think why your friends BCG my work better is because it is newer and not worn down.

thanks

#7 ky2970

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Posted 31 December 2012 - 12:17 AM

Long story short, for me, the piston was not making an airtight seal in the bolt carrier group. This isn't something you will have without modifying your bolt carrier. For the jams, I suggest tightening the screws that attach the outer barrel to the inner barrel.

#8 akiraspeedstar

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Posted 31 December 2012 - 08:18 AM

What modifications did you do to your BCG? Also remove the piston (small c-clip on the rear) and change the OEM o-ring with a green harbor Frieght O-Ring.

#9 ky2970

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Posted 31 December 2012 - 07:54 PM

I already edited the post but earlier I had a post about rounding out the area near the bolt carrier where it contacts the hammer. I rounded it out too much and breached the piston. I already fixed the post though so no one makes the same mistake! As for the HF O-ring, I will definitely get a set to replace the OEM one.

#10 General Pickle

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Posted 01 April 2013 - 08:55 PM

Hey guys, necro post here, but I'm having very similar issues with my barely used (brand new when I got it, I've only put maybe 500 rounds through it at the most) LM4 PTS. It has major inconsistency when rapid firing on semi or especially on full-auto. When the hop-up works right it sends .30g biovals out to probably 200ft+ but then it will randomly drop a BB 5ft out or give me a double feed. The only mod I've done was replacing the o-ring with the HF o-ring, but that was done in hopes of solving this problem. I also have a new flash hider installed, which I thought could be putting stress on the barrel but after a close inspection that is clearly not the case, plus this issue was happening when I hadn't taken the stock flash hider off as well. What could be causing this?

#11 Chuck S

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Posted 02 April 2013 - 02:53 AM

The issue with my stock LM4 was very similar to yours and was fixed under warranty by KWA where (as I recall) the bucking, and maybe the hop up was replaced and there was an adjustment inside the bolt carrier judging from the scratches on the rear of the carrier around the lil' C-clip.  Been working fine ever since.

To get to the bucking requires removing the barrel and that is fraught with the potential to damage the multi-piece upper receiver if the Locktite isn't melted first.  There are several threads on this.  Be careful.

KWA has all the parts in hand and can make the repair very easily.  Self repair usually has be guessing what parts I need.  Note KWA will not service the gun at all without the orange tip compensator on the barrel.

-- Chuck

#12 R_King91303

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Posted 02 April 2013 - 05:44 AM

Try replacing the C-clip with an o-ring to see if you can get a more consistent seal within the piston. If you bought the HF black (nitrile) o-ring kit, the smallest o-ring in the kit does the job.

If that doesn't work, then send it in to KWA for a more comprehensive inspection to see what the problem could be.

Posted from my iPhone

Edited by R_King91303, 02 April 2013 - 05:46 AM.


#13 General Pickle

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Posted 02 April 2013 - 06:25 AM

I've been running my gun with propane and biovals though, so will they still take it? Obviously it won't be under warranty but would they still do it?

#14 BeachEMT

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Posted 02 April 2013 - 08:10 AM

Yes, they will service it even if it isn't under warranty. Just submit a request on the help desk.

#15 R_King91303

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Posted 02 April 2013 - 03:09 PM

Bioval's void warranties?? I thought the only things that voided warranties were propane usage and/or mechanical (operational) modifications??


Posted from my iPhone

#16 BeachEMT

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Posted 02 April 2013 - 03:28 PM

I think he was just informing us what "ammo" he uses. Biovals do not void warranty. I think it's just propane, removing the orange tip, modifying parts and abuse (ie. dropping or something).

#17 General Pickle

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Posted 02 April 2013 - 04:41 PM

I don't see why the BB's would void the warranty, however I could also see why KWA may see that as a viable reason not to honor the warranty; if somebody used cruddy .12g BB's and jammed their gun then clearly the BB's were not up to spec, and since the recommended gas/BB's are only KWA brand it wouldn't be too far fetched to think that it would void the warranty. Anyway, I've submitted a help desk ticket and waiting for a response. I'm very confident that the issue is due to a faulty part since this problem has been happening ever since I got the gun, regardless of BB's or gas or o-rings.

#18 gcw360

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Posted 02 April 2013 - 07:27 PM

Biovals do not void the warranty...they are quality BB's.

#19 DarkKing

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Posted 14 July 2013 - 08:00 PM

Hey ky2970,

I've got the exact same problems with the BCG; I did the modification you suggested with the UBR stock and now my gun short cycles and jams; I then bought the Bushnells CAR buffer tube that was suggested but that didn't seem to do anything for the gun. The bolt locks back after firing just 3 shots, the gun jams and I want to fix it but have no idea what to do. I've got a local shop that charges $40 an hour for repairs which I'd rather not do. If you could please do a step by step tutorial on exactly how you fixed the issue due to modifying the gun for the ubr stock I'd really much appreciate it, I don't want to buy a $50 BCG and screw it up again. Thanks for the time

-Win

#20 ky2970

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Posted 17 July 2013 - 12:30 AM

It wasn't the UBR stock modification that caused my jamming. Could be something else with the gun?




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