M4 Not shooting

[Noctis]

Hi docs,
I recently had to change the gears of my Ares M4 as one of them lost two teeth. So I got my gearbox up and running, everything's assembled and looking good, the gearbox IS shooting compressed air, but once I lock a mag into place (the mags are feeding, and a BB gets jammed in the hopup), I can try to shoot but nothing goes and my gun sounds like its silenced. I made sure the barrel is clean, the hopup is ajusted to a reasonable level, I'm really all out of ideas on this one.
Thanks docs
Noctis

[Azathoth]

A couple of things can cause your problem

1) did you do a compression test? Take the cylinder, piston and cylinder head in your hands and block the cylinder head port with your finger while pushing the piston into the cylinder. The Piston should get stuck from compressing air. If it isn't you have a massive air leak. Repeat this test but add the air nozzle.

2) Some hopup rubbers are too stiff or put too much friction on the BB. Take your assembled hopup unit out of the gun. put a BB in to the back end and load it. And then try pushing the BB out through the barrel with a un -jamming rod. If it's at all difficult to pass the BB through your hopup system is putting too much pressure on the BB.

3) Your tappet plate spring is not installed.

That silenced sound that you hear is the lack of air exiting the muzzle of your gun. Instead, it is exiting where ever it can probably somewhere just in front of the air nozzle or back into the gearbox through though the PH oring. This can lead to stripped pistons