VFC M4 Compression Issue?
 

Hey

So here's what's up, my VFC M4 suddenly started shooting ~200 fps, which is odd because the time I had chronied it before that it was shooting at about 380. Someone had told me that it was a compression problem, but unfortunately didn't tell me much more than that. What exactly does a compression problem detail to? What parts are necessary to fix this?

Thanks

things to check
cylinder head o-rings
piston head & its o-ring
loading nozzle & the nozzle tube on the cylinder head
hopup sleeve

Have you replaced anything on the gun recently? Removed the upper reciever with the hop up and barrel?