KJW M4 issue ***solved***

[waltherglocksmith]

Got a malfunction with my M4 KJW,

after firing a complete magasine, the bolt stay back and the bolt release button (on the left) is engaged. (normal operation, everything fine at this step)

Then, I load a new magasine with full of bb's, and I push on the bolt release button, and the bolt does not close completly, like if the spring is too weak. So I push with the foward assist button to close completly the bolt,

and it not work, once I pull the trigger, one bb goes out slowly and i can hear the gas emptying until I remove the mags.

When there is no bb into the mags, the bolt release button works fine and close the bolt completly.

So each time I empty a mags, I need to push the button (with no mags inserted), then add a new fully loaded mags, then arm it with the bolt catch handle at the rear.

any idea???,
thanks!

[Windows]

I had a similar problem with a high cappa. Check to see if the loading nozzle is bent or broken as this can cause it to jam when the BBs are under the pressure of a full mag.

[Canadian Psycho]

Lube everything, including the spring guide in the buffer tube. check the return band on the bolt, to make sure its not broken.

[Saberwing]

Could also be that your feed lips are really tight as they are on mine. I had the same problem.

[waltherglocksmith]

loading nozzle is OK, the gun is new.
I just make few test right now, and notice that once it happen (it happen once every 5-6 mags and what cause the bolt to stay open is a jammed bb just below the chamber, so the bolt cannot close and stay opened. Removed the jammed bb and looked at it, and he is badly dent each side.
Maybe this gun need break in period? anyway, it shoot awesome!

[waltherglocksmith]

Could also be that your feed lips are really tight as they are on mine. I had the same problem.

Whad did you do to solve the problem?

I will lube everything and try again.

thanks all for your help!

solved after light cleaning, no more problem