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Piston sticking in Bolt Carrier

piston bolt problem

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#1 crazyfox

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Posted 12 February 2013 - 07:06 AM

I am having a strange issue with my new LM4.

I think the piston is meant to stick in the chamber for a second when the bolt is retracted and then spring back, correct? Well mine does this only sometimes. Other times, the piston is stuck inside the bolt and moves with it. Also when the bolt locks back, the piston will frequently be sticking an inch or so forward out of the bolt. Is this a common issue? The hop up is off, I changed the oring on the piston for a HBF P014, then changed it back again to the stock one and the problem is still happening. I have been using this, http://www.homedepot...51#.URpaFqVX0s4 and the piston is well lubed.

If I need to take some pictures I will later. Any help would be appreciated.

PICTURES!

What I believe is meant to happen
Posted Image


And what actually happens
Posted Image

Edited by crazyfox, 12 February 2013 - 11:54 AM.


#2 Chuck S

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Posted 12 February 2013 - 07:23 AM

A little silicone lube do anything?  If the O-ring is too tight the bolt wil bind.

-- Chuck

#3 Theshank

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Posted 12 February 2013 - 07:38 AM

Clean all that lube out of there, get a fresh o ring and use 30wt silicone oil, then try it.

#4 crazyfox

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Posted 12 February 2013 - 08:07 AM

Will silicon lube swell the Oring? Or is that only spray? I have plenty of Harbor freight P014s so I guess that isn't a huge concern. I will try to get some and use that.

#5 crazyfox

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Posted 12 February 2013 - 11:56 AM

UPDATED WITH PICTURES! Some more information as well.

When it gets stuck in the Bolt Carrier, as seen in the second picture, I have to use my finger and apply a bit of force forward until it suddenly dislodges itself and then begins functioning normally. It's like it is hanging up on something inside the bolt. After racking the charging handle a few times, and will begin getting stuck again.

UPDATE:
I took apart the BCG again (I'm getting really good at removing that little C Clip) and wiped down the entire piston, removing all the lube. It now seems to function correctly. I think the lube was too thick and may have been causing a bit of a suction effect or something similar. It may also just be a break in type issue and more rounds need to be fired. Time will tell.

Edited by crazyfox, 12 February 2013 - 12:20 PM.


#6 akiraspeedstar

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Posted 12 February 2013 - 02:17 PM

Holy crap! I didn't seem those pics before that's a lot of lubricant! Really you just need it for the seal, that's REALLY excessive. Also if the rear seal for the piston becomes gummed up or dries out it can also cause the piston to stick inside. You also seem to have a lot of lubricant in the hopup area, I'd clean all of that out of there as well.

Edited by akiraspeedstar, 12 February 2013 - 02:18 PM.


#7 Theshank

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Posted 12 February 2013 - 06:27 PM

Looks like the bucking rubber is coming out on hop up teeth. In the front.

#8 crazyfox

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Posted 12 February 2013 - 08:31 PM

Yep akira, I got a little overzealous with lubricant. It is now pretty much bone dry. I will wait until my silicon oil arrives. Do you think this will work alright? http://www.homedepot...51#.URsWwaVX0s4

Theshank, I can assure you that isn't the rubber. I too was pretty concerned after looking at that picture. But it's simply the angle at which the picture is taken that the upper receiver appears that way, it's a bit of an optical illusion.

#9 ky2970

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Posted 13 February 2013 - 06:26 AM

Is there an actual difference in performance?

I notice with mine, sometimes the bolt will do as it's supposed to and other times it won't. But it hasn't affected the performance in any way.

#10 crazyfox

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Posted 13 February 2013 - 06:52 AM

When it was happening a lot, the recoil was slightly less and the fps was reduced slightly. I can't speak to range or accuracy as I don't have anywhere to shoot it outside yet.

#11 -wigs-

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Posted 15 February 2013 - 09:45 AM

I would stay away from any lube at he depot.
Go to a hobby store or any store that sells rc cars and buy 30wt pure silicone shock oil

#12 crazyfox

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Posted 15 February 2013 - 07:03 PM

A lot of people suggest super lube though. Am I wrong in using that?

#13 akiraspeedstar

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Posted 15 February 2013 - 07:15 PM

They suggest super lube Dri-Lube for the bolt carrier.

#14 gcw360

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Posted 15 February 2013 - 09:51 PM

That's what I use....

#15 crazyfox

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Posted 15 February 2013 - 10:00 PM

Also T-Hum, the KJW M4 god suggests the Super Lube synthetic grease. I figured, similar platforms so why not.

Edited by crazyfox, 15 February 2013 - 10:01 PM.


#16 gcw360

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Posted 15 February 2013 - 10:13 PM

View Postcrazyfox, on 15 February 2013 - 10:00 PM, said:

Also T-Hum, the KJW M4 god suggests the Super Lube synthetic grease. I figured, similar platforms so why not.
The Super Lube synthetic grease is better suited for AEG gears and large parts.

#17 crazyfox

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Posted 16 February 2013 - 08:24 AM

Alright, noted. Thank you. Also with the dri-film (I have ordered some and I am awaiting its arrival) should I completely wipe down the bolt carrier and apply it only to the steel portion? I think that's correct.

#18 gcw360

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Posted 16 February 2013 - 08:53 AM

View Postcrazyfox, on 16 February 2013 - 08:24 AM, said:

Alright, noted. Thank you. Also with the dri-film (I have ordered some and I am awaiting its arrival) should I completely wipe down the bolt carrier and apply it only to the steel portion? I think that's correct.
I only use it on the outside of the BCG.  So, yes, whipe it down and apply the Dri-Film.

#19 jonsun81

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Posted 18 February 2013 - 10:10 AM

How easily is the nozzle supposed to be moving in the bcg?  Because when i use a hbfr oring the compression is very weak but the nozzle moves about freely and when i use a danco 10 the compression is amazing but takes a little more effort to get it to snap back into the bcg.  

Danco the nozzle stays in the bcg when i pull the charging handle back

Hbfr the nozzle stays forward as the bcg goes back and then snaps back into bcg





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