ICS M4 Commando (MK18 mod 0)

My end goal with this build it so make a MK18 mod 0. I will not, however, be doing a exact replica.

Being a ICS M4 this has a split ver. 2 gearbox, and I intend to have 2 upper gearboxes; one that shoots at 450 fps with .20g bbs, and the other at 300 fps with .20g bbs.