Low FPS with m120

[darkaces07]

I have a G&G asgi "custom" gun. When I got the gun it wasn't shimmed right so I reshimmed the gearbox and put in a M120 spring. It would not shoot thru cardboard. I took the gearbox apart and tested for compression there was no compression i only felt air coming out the back of the cylinder. So I tried a different piston head and cylinder head and I still don't have any compression. I then tried a different cylinder I have good compression with a piston head from a AGM gun but terrible compression with the G&G piston head. I swapped the o-rings and still no compression with the G&G piston head. I would swap the cylinders but my gearbox has pneumatic blow back so im stuck with the G&G cylinder. Anyone have an idea on what is causing this to happen

[GacktC]

If I am not mistaken, the mechbox of the G&G blowback aeg is a copy of the TM blowback guns.
The spring guide is sitting all the way in the back compare to the old Ver2 mechbox, so you probably need a stronger spring (or even the original spring).
Since it is a newer type blowback Ver2 mechbox, only Laylax & Systema make upgrade parts for it.

[Beran]

or yotu could go to ace hardware and find a new o-ring that fits and gives good compression for like a quarter.

[league 4]

If I am not mistaken, the mechbox of the G&G blowback aeg is a copy of the TM blowback guns.
The spring guide is sitting all the way in the back compare to the old Ver2 mechbox, so you probably need a stronger spring (or even the original spring).
Since it is a newer type blowback Ver2 mechbox, only Laylax & Systema make upgrade parts for it.

No, G&G's is different. But Beran's right, it just sounds like you need a new O ring.

[darkaces07]

Alright thanks guys I will go to Ace hardware today

[CommieHunter]

It may be the piston head. The G&G piston heads sometimes leak through the middle screw.

[Nec]

It may be the piston head. The G&G piston heads sometimes leak through the middle screw.

If I recall correctly G&G piston heads have their screw's inside their piston.

[MattK42]

Yea, ditto on the o-ring. They're cheap too(60 cents for two at the local hardware store.) Make sure you get the correct size. Which I believe is #14, that's what I've used whenever I've had to replace an o-ring.

[CommieHunter]

Perhaps new ones do, but the last couple I worked on didn't.

I only see G&Gs that are broken, so I can't say how many don't work, but the last two I worked on had a screw from the front, and it was leaking through that hole.

[league 4]

These are the most recent ones... Or at least they are in the AK's, m14's, and M4's. I don't know about the rest.

[Raging Hormann]

Neat design.