Mag won't expel gas for blowback.

[Asomodai]

Hello all.

Problem with one of my TM FN57 mags.

Got a TM FN57, only part that's changed is the outer barrel.

One mag fires with no real issues. Other mag, I rack the slide and although a BB fires out (low power) the slide won't blow back and I have to manually rack the slide to fire another BB (Again with no power) mag is full of gas. 

Any ideas? 

Using green gas. 

 

[Guest]

Does the input valve have a silent fill o-ring? If it does, take it out

or
 

Poor gas router to nozzle seal

or

Damaged output valve

 

[Crome]

Does the input valve have a silent fill o-ring? If it does, take it out

or
 

Poor gas router to nozzle seal

or

Damaged output valve

Gotta love that this is so much not your first rodeo that your advice now reads like a choose your own adventure book lol

 

[Asomodai]

Does the input valve have a silent fill o-ring? If it does, take it out

or
 

Poor gas router to nozzle seal

or

Damaged output valve

Solved! 

Sticky output valve which wont return to position fast enough. Still in Cornwall without tools so had to use spit instead of silicon as lube. Firing every time now. Until the spit dries out anyway.