One of the really cool things about dropping a Retro Arms gearbox into a VFC SCAR receiver is that with a couple of small modifications you can have a true quick-change spring with ZERO removal of the gearbox required.
Installing the Retro Arms CNC gearbox shell requires a modification to the lower receiver to allow it to sit level – basically the removal of about a 1/2″ of polymer material (a “shelf” if you will) from inside the magazine well.
I ultimately decided not to drop a MOSFET into this gearbox since I wanted to retain the ability to remove the lower and not have any ugly wires snaking through the buttstock hinge area (which also creates a potential pinch point). So I removed all of the stock wiring harness, as well as gutted the wiring from the buttstock and ditched the fuse. I rewired the entire thing with 16 gauge Deans ultra-wire and reused the VFC contact pins and electrical contact hardware in the stock. Overall it makes for a really clean look; and coupled with the high speed gearset and the Systema Magnum motor it has excellent trigger response.
Internals list:
– Retro Arms CNC 8mm QSC gearbox
– FLT 8mm bushings
– Echo1 selector plate
– Lonex trigger switch
– Siegetek 14:09 gearset
– Lonex anti-reversal latch
– SHS cutoff lever
– Lonex extreme tappet plate
– Lonex double o-ring aluminum cylinder head
– 3/16″ Air-Pad
– Retro Arms POM piston head
– SHS 14 tooth AOE corrected piston
– VFC air-nozzle
– Unported brass air cylinder
– Prometheus M135 spring
– Systema Magnum high torque motor w/new pinion gear
– 16 Gauge Dean’s Ultra Wire
