Shoei MG-42 PolarStar Fusion Engine Conversion

28-IMG_2053The Shoei MG-42 AEG is a relatively rare airsoft gun. It’s a high quality replica of the classic WWII German machine gun. Mike Alexander wanted to take his AEG powered MG-42 to the next level and so he sent it out to have a PolarStar Fusion Engine installed. Ultimately his MG-42 will be mounted on the back of a tracked vehicle (watch this space for pictures when available), so the gun was setup to be powered by a SCUBA tank to provide an ample supply of HPA, without worrying about the extra weight of the large tank.

08-IMG_1983The Shoei MG-42 gearbox design is unique in that the gearbox shell is actually part of the gun externals. The gearbox has two parts. The piston and cylinder are located in the main body of the gun, while the gearset and motor are in a detachable grip assembly. The grip of the gun is essentially gearbox shell, with a couple of plastic grip plates covering it up on each side. The trigger assembly is also integrate into the grip section.

24-IMG_2035Since the gun is so rare (and expensive!) I wanted to try and maintain the integrity of the gearbox shell with the installation of the Fusion Engine. So the solenoids were moved outside of the gearbox shell and minimal milling was done on the Fusion Engine and the shell to allow it to fit inside. 23-IMG_20343D printed parts were used to hold the solenoids and the mini circuit board, which kept everything nice and tidy. The remote placement of the solenoids, though, required extra long air lines, so the FCU settings had to be adjusted accordingly to allow enough air to flow through the solenoids to actuate the nozzle and poppet valve.

11-IMG_1987It turns out that having the Fusion Engine installed inside of the gearbox shell put it in a perfect position so an unmodified P* SCAR H nozzle could be used.

The trigger activates a small microswitch, so it was easy to add wire connectors to link it up to the mini circuit board and then on to the FCU via the wire harness.

The mini circuit board is mounted to a 3D printed bracket designed to make it low profile so the receiver can be closed properly. The bracket is attached to a pin that runs through the gearbox shell. In the AEG version, a metal pin is used to hold the spring guide in place, so it was used to now hold the solenoid bracket in place.

34-IMG_2062The FCU was attached to the top of the gearbox to make it easy to access for adjustments. The 7.4v LiPo battery that powers both the FCU and the drum mag is located in the stock.

The drum mag appeared to be a real drum mag modified with a hi-cap magazine and servo to auto wind the high cap. The drum mag had a slide switch added to it activating the winding mechanism. With the Fusion Engine conversion, a MCU (motor control unit) circuit was added to link the FCU to the box mag, so it will now wind automatically when the trigger is pulled.

36-IMG_2065The drum mag feed spring goes into the front of the gearbox shell where it had an integrated BB feed tube up to the hopup. The original feed tube bracket appeared to be missing, and a piece of white plastic was used to try and hold the spring in place. This part was replaced with a custom 3D printed bracket that reused the original mounting point and incorporated a screw clamp that will positively lock the spring in place.

The MG-42 was uses a G&G M14/AUG style hopup unit. The barrel was upgraded with a 650mm Madbull 6.03 barrel and Maple Leaf bucking.

38-IMG_2069To power the Fusion Engine, a SCUBA tank is going to be used. To make this work, a SCUBA fill station is attached to the tank. Then a fill whip is used to link the fill station to the fill port on a small 13ci Ninja HPA tank. Attached to the Ninja HPA tank is a Ninja LPR air rig matched with an 8 foot big bore air line from Amped Airsoft. So as the air is used up in the small Ninja HPA tank, it is continuously recharged by the larger SCUBA tank. Multiple SCUBA tanks can also be cascaded together to provide an effectively unlimited air supply.

Mike now has a reliable, high performance Shoei MG-42 to mount on his vehicle. With the Fusion Engine and the large air supply, the crew manning the gun station will be able to deliver a lot of firepower as they prowl the field! They’ll need to keep a large tub of BBs close at hand. 🙂

Happy Airsofting!

– Rudy