HPA GBB TM MP7 feeding issue

[JammyBeth]

Just got a brand new tm mp7 gbb, fixed it up with an airtac m4 adapter, started shooting, and I’m having an issue where unless I keep the mag (+adapter) pushed into the gun, it eventually starts firing more weakly, and only on every other trigger pull

 

Seems to work a bit better when it’s oiled up, but usually only temporarily.

 

Unfortunately I can’t actually test anything out for a while (although I do have the original gas mag I cannibalised that I could rework to test it), but would appreciate help diagnosing the issue. 

 

(My suspects so far are:

-valve knocker malfunctioning (either on mag or gun)

-gas route seal is dodgy (I have some other gas mags, non-mp7 I could potentially try?)

-dodgy feed lips

-regulator too low, bolt not cycling

-something to do with the magazine catch?)

 

I’ll probably next test it (with HPA) in a couple of weekends’ time, and if nothing helps, I’ll just have to send it off to the techs at my local place (apparently they’re pretty good), but it would save me my pride, and potentially enough money to buy a used revolver I’ve got my eye on if I could fix it myself.