SYEK, that's a nice looking barrel, but the only reason I'd take the SV barrel over that is that the ed is threaded on the SV barrel, allowing you to put maybe even a 300mm suppressor on. Also, I don't think you'd need another lower receiver if you wanted DM/AR. For the gearbox, I'd go with a silent piston head, helical gears(yes horrible to shim, but more quiet, Use inside/outside calipers to find the amount of shimming needed. That's what I do) And maybe a silent grip. I've only heard about them, but apparently they quiet the motor which is a lot of the noise you hear when firing. Also, if a