Update: GHK 553 GBBR Sneak Peek and Demonstration from RWTV
Marck from RWTV got the latest prototype from GHK new GBBR 553, however it’s not final version, but from the preview we can see it has 3 fire modes: semi, burst, auto, and one more important thing to be noticed is that the bolt is only half travelling, same as GHK’s AK GBBR series. For more demonstration, you can check post on Facebook (source 1, 2) and Youtube.