Trigger only cycles piston a few mm at a time?

[Airsoft-Ed]

So, a mate at Uni has an issue with his M4.

In his exact words:

"it takes about 5-7 trigger pulls to fire, each one pulls the spring back a little further then eventually fires, do this a few times then she works fine if keep firing every so often but as soon as u stop for over a min or so she locks up again and the everything starts from the beginning"

Any ideas?

My thoughts are that either the motor is screwed, or there's some sort of resetting issue with the cut off lever, could the spring on it have gone or something? My L85 cut off works differently, so I'm not totally sure how it works on an M4.

He's never taken a gun apart and he's reluctant in case something goes wrong or he loses a part. Plus, you can't fix something if you've never seen it working before. So we can't diagnose it by asking him to open it, and he's too far from me for me to do it without some idea of what the issue might be, 'cos I hate V2 boxes.

So, thoughts, experiences, fixes?

Hit me.

Cheers.

 

[sp00n]

Has he increased the motor pressure on the screw on the pistol grip at all?? Back it off see what happens.

Other thoughts:-

Try a different battery

Check the battery connectors etc

 

[Airsoft-Ed]

I'll ask him about the motor height adjustment, but I've have expected him to mention it making a different noise if that were the issue and since he hasn't I wrote it off as being the problem. I can't really see how that'd produce the symptoms he's described either. It'd either spin freely, or just go really slow and sound horrible.

Worth a shout though.

 

[sp00n]

I'll ask him about the motor height adjustment, but I've have expected him to mention it making a different noise if that were the issue and since he hasn't I wrote it off as being the problem. I can't really see how that'd produce the symptoms he's described either. It'd either spin freely, or just go really slow and sound horrible.

Worth a shout though.

Click to shrink...

with vibration, and depending upon thread direction some guns wind themselves in and some wind out, if they are not lock tighted in place. as a source from my idea was when i first reassembled my MP5K i didn't set the motor height, and still being set to the original TM setting it was too high ... this produced similar results as to what your friend may be seeing, as you needed the initial burst of power to overcome the mechanical friction. It is also the easiest thing to check, with out disassembling the rifle

next up on my hit list of things to check is the plastic selector plate on the side of the gearbox, and/or something with the cutoff lever (spring maybe), and then trigger its self.

 

[RR01]

I had exactly this on an M4 I built from parts. From memory, I think mine was a trigger contact issue. If I'm remembering correctly (it was a while ago) the moving trigger switch wasn't contacting the fixed blades on the trigger contact for more than a fraction of a second, because it wasn't sitting right in the switch unit and kept jumping out of contact with the top part of the trigger itself. A weak return spring didn't help either. As your friend has found, each pull of the trigger only connects the motor for a very brief period, not enough to run a full circuit, although occasionally it will connect and run properly.

My guess would be to replace the V2 trigger switch with a new one, as the fixed trigger contacts may also be partly burnt away.

 

[Pointman PUG]

Trigger contacts bruv

 

[sp00n]

is auto working or is it on both auto and semi?