M4 sporadic firing

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MisterC

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Hi all, posting this on behalf of my brother.

He recently bought a G&P M4 (second hand), running on a 7.4v LiPo via a rear deans connecter, and is having trouble with intermittent firing.

It fires for varying lengths of time before there is no response, sometimes getting through a several hundred rounds, sometimes only a handful before there is no trigger response.

Moving the crane stock/disconnecting and reconnecting can sometimes sort the problem momentarily, but is only a very temporary fix.

When it fails, there is absolutely nothing from the trigger; no clicking, no buzzing, no grinding or anything of the sort, but can restart without any warning either...simply one moment it will work fine, then the next it wont.

Anyone have any ideas what the problem might be or any advice on how to fix it? Please bear in mind we are both pretty new to airsoft and have never opened a gun up before.

Anyone with advice which leads to a fix will be greatly rewarded in the next life.

Thanks
 
Check the motor connectors are on properly.

Are you handy with tools? it's going to most likely be a connector issue, rather than a 'box issue. Check the wires aren't stripped anywhere and shorting

 
Yep +1 on it being a wiring issue. You'll have a loose connection/solder or short somewhere.

 
Sounds like dodgy wiring at the rear somewhere. My money would be on either a bad connection in the battery connector or it's damaged as the wiring goes into the body. Get it sorted soon if you're running a LiPo - shorting out a LiPo can have pretty bad results!

 
The other possibility is that the disconnect on the trigger contacts may have a weak return spring in it, so that when you release the trigger the contact doesn't fully return to the start position. This means that when you pull the trigger again is doesn't connect with the moving contact to press it into contact with the fixed copper contacts. Had this happen with my G&P M16 a while ago.

If it is this then you'll need to strip the gearbox, not something to do if you have no experience as you can loose all the parts if you try to open it without holding it all together until the main spring is removed.

 
Thanks for the replies.

We've posted in other places and the general consensus seems to be that it's either a break in a wire, loose connection, or something faulty/failing on the trigger.

Never thought about the possibility of the lipo shorting...i'll be sure to pass on the warning to him(y).

I'm half devent with a soldering iron, but have next to no idea what i'd be doing with it inside an airsoft gun, and we're not gonna even try fiddling with the motor, so we're gonna have somebody who actually knows what they're doing have a look at it next week, hopefully to get it sorted in time for its first skirmish on sunday...fingers crossed...

.

 
Just a quick update guys.

I took it to a shop to be looked at (crafty's airsoft in Derby) and they opened it up to find the plugs to the motor had been soldered on by the previous owner, and one had come off, so was making, then losing contact with the motor intermitently. They replaced/refitted them properly and it seems to have done the trick, but we'll know for sure come game day sunday

Thanks for all the suggestions, but Rock-climby-Dave was the winner on this one, so many man points to you, Sir.

 
It is quite literally my professional job. So at least I'm doing something right!

No noise from an AEG is almost always a loose connector (especially an intermittent lack of noise) and is ALWAYS better than a grindy noise!

 
Yeah, we were both pretty content that a gun not firing is better than a gun making a grinding noise.

He skirmished it yesterday and it held up just fine with no glitches at all, so good news all round.

 
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