Extremely low FPS!! Airsoft AEG, What caused it?

Video investigating the reason for really low FPS in airsoft AEG. Ares KM9 is the airsoft RIF in this video.

Background music:

Max Brhon - Pain [NCS Release]
Music provided by NoCopyrightSounds.
Watch: https://youtu.be/wf3XPionPXE
Free Download / Stream: http://ncs.io/MBPain