G&G L85A2 AFV - cylinder volume
 

Tore apart my new L85 AFV today which has a 300mm inner barrel. Getting low fps on an m120 spring - approx. 375. Air seal everywhere is solid.

The suspected issue is that it comes with practically a full SR-25 lenght cylinder with barely 5-8mm of porting on the end.

I have no SR-25 cylinder experience but guessing a 3/4 port might be best in this case?