CA M15A4 Low FPS

[TrainsCDG]

High guys

I bought a 7 year old Classic Arm M15A4 from my local airsoft shop monday. I found that I needed to replace the piston which was missing teeth and the spring which used to be a M100 but had been cut. When I took it in today the FPS registered as 0,0,174,175,0,174,0,175. It was a bit confusing what this meant and looks to possibly be a problem. The range is also really terrible but accuracy is fantastic. I have looked for solutions but the answers don't help. Anyone have any ideas? I really want to get this working as it is a fantastic gun.

[Lee 303]

Re: CA M15A4 Low FPS

Did you check the compression when you had the gearbox open
I would have replaced the piston head O-ring as a metter of course to ensure compression way 100%

[TrainsCDG]

Re: CA M15A4 Low FPS

It was a brand new piston bought the same day. I have also fitted a new motor, hop up and hop rubber. I will check the compression next time I can open it (going away for company training for a week).

[Lee 303]

Re: CA M15A4 Low FPS

The O-ring is part of the Piston head and most pistons come without the piston head attached
Did you re-use the old piston head with its old O-ring ?