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Weird issues on LM4 PTS


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#1 pingupenguins

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Posted 10 May 2013 - 12:21 AM

So I'm having some strange issues with my LM4 PTS. Never used it in a skirmish, just for plinking.

When I put the gun on full auto and try to mag dump, I can't get through the mag without the gun randomly stopping. Then I switch it to semi and it leaks a tiny bit of gas out the barrel. The Bb kind pops out and lands 10 ft in front of me then gun does a full cycle and the same thing happens when I put the trigger in semi. So its leaking a little gas out, then firing and it keeps doing it. If I rack the bolt back with my finger on the trigger, the bolt fires back like normal.

Only mods were the Bolt catch mod, and ramping the nozzle area on the BCG to keep the air nozzle from ever locking forward.

I was thinking it might be a mag/valve problem and a little lube might help it. But I don't have a second mag to confirm it is the mag and not the hammer.

Let me know what you guys think. Btw, any one got extra Green oring from harbor? I would like to install it to maybe fix any gas leaks.

I'll try to get a video up tomorrow.

#2 General Pickle

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Posted 10 May 2013 - 12:42 AM

Mine had a very similar issue, to which I believe I can attribute the issues in mine to either the nozzle getting stuck forward or too much lube (fairly thick lube at that) or maybe a combination of the two. What lube do you use and how much? The bolt stop mod is a good idea and so is the ramping of the BCG by the way, so I don't think that would be your issue.

#3 pingupenguins

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Posted 10 May 2013 - 08:21 AM

I may have gone a little crazy on the lube inside the nozzle area. I put a lot of lube on the O-ring since it has a horrible seal. Did the same thing to the KJW Hi-capa, no problems.

I'll clean it out and be less liberal with lube. I don't think the nozzle is getting stuck forward. I made sure it wouldn't. Hopefully its just lube then.

#4 pingupenguins

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Posted 10 May 2013 - 03:05 PM

Seems to be fixed now. Added some lube to the metal piece + o-ring that goes into the plastic nozzle (not the rocket valve). Wasn't locking to the rear though until I figured out that I forgot to put in the locking tab..........

#5 R_King91303

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Posted 10 May 2013 - 08:11 PM

You mean the C-clip? I got rid of it and replaced it with an o-ring. Makes maintaining the green o-ring much easier. I also think it
made the cycling of the bolt more efficient because before the mod I would occasionally get a run away bb; bb that dislodged from the hop-up and would roll out the end of the barrel if it was pointed towards the ground.


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#6 BoobieM4H

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Posted 12 May 2013 - 07:21 AM

You gotta let your ONE mag cool down and get back to close to room temp..or else you'll freeze your nozzle and oring up and cause it not to cycle correctly. Which it sounds like its doing the delayed Blowback as you described. Buy a couple more mags if youre just plinking. By the tine you shoot through 3 or 4 mags..the time it takes to reload and gas them up should be enough time to let then cool down too

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