Another guest submitted story to Hyperdouraku by Gunsmith Baton and this one covers the LCT Airsoft STK-74 AEG. Released last 20 May 2016, it is sold as complete AEG and the receiver and stock are also sold separately for those who are interes in these parts. The Version 3 Gearbox has 9mm bearing and the AEG package comes with a 130-round magazine.
Read more about it here (in Japanese).