WE G18c Mag Venting Gas

[Chonty]

Hi everyone, new here and would really appreciate help,

One of my extended mags for my WE G18c is venting all the gas on cocking the gun. On inserting, it vents a tiny bit, then i cock the gun and all of it comes out. I'm using Nuprol 2.0 green gas, so the silicone oil should have lubed the mechanism quite well. I have tested cold and warm, same problem. But i have 3 other mags with which this doesn't happen, so I'm thinking maybe the valve?

Any Suggestions?

Thanks loads

 

[GeneralKimbo]

Yeah probably need to replace the o rings or something.