After several months I'm finally coming back to airsoft and pulled my WE-Tech AKS74 out to run some maintenance and tests to ensure it was field ready. It's been mostly untouched since my last game in October which it operated perfectly fine with zero issues.
Back then, I installed an RA-Tech NPAS to lower the FPS just under my local fields limits since the stock valve shoots fairly hot out of the box. But coming back to it now, I find that when test firing the BBs consistently fail to shoot out and frequently bunch up or roll out of the barrel. The bolt still cycles back, pushing a new BB into the chamber but again it fails to send it through the barrel.
I tried adjusting the NPAS every which way from the lowest setting to the highest but I still got the same unfortunate results. Oddly on occasion, BBs would find themselves stuck in the receiver itself without ever finding their way into the chamber and would jam the bolt carrier preventing it from closing. This became more clear when pulling out the magazine to clear the replica and BBs would fall onto the ground. Still unsure how that is happening, the nozzle itself isn't damaged and should be guiding the BBs from the magazine into the chamber perfectly fine.
Hopup was also set to the lowest, figuring that it might've been the hopup keeping the BBs stuck in the barrel but no that was not the culprit.
With no other options, I pulled out the NPAS and reinstalled the stock valve. Shockingly this worked and it fired BBs normally and operated smoothly without any of the previously stated issues. I tried again, swapping out the stock valve with the NPAS and ran into the same problems even with the NPAS set to the same rough size as the stock valve. Like I said before, it worked perfectly fine last year with an NPAS. No internal modifications have been made since besides upgrading WE's crap trigger group to steel parts.
I ran the same test several times over and got the same results, the NPAS seemingly decided it wants to screw me over now. I'm completely stumped and now considering modifying the stock valve.
Anyone got any clue what's going on?