When it comes to internals allowing this full metal M4 AEG to shoot up to about 410 FPS with 0.20 g seamless BBs .
Internals are a full metal gearbox ( with 8mm double bushings and spring guide with bearings ) is compatible with aftermarket Version 2 parts .
When it comes to internals , a full metal gearbox ( with 8mm double bushings and spring guide with bearings ) is compatible with aftermarket Version 2 parts , allowing this full metal M4 AEG to shoot up to about 410 FPS with 0.20 g seamless BBs .