The MP40 airsoft gun uses a very unique gearbox design. To have the Fusion Engine fit in the gun, the existing gearbox shell was cut and milled to house the V2 Fusion Engine upper cylinder. The stock trigger switch was removed and replaced with a microswitch so there would be room for the valve air lines. The fire select was also handled by adding a microswitch which is activated by the full auto selector plate lever.
The design of the MP40 allows for room behind the gearbox to house the battery, which provided plenty of room for the FCU and a small lipo. A mini circuit board was used to link all the switches to the wire harness, and a custom length nozzle was needed since the engine was installed set back from the front of the gearbox face.
The MP40 also has an interesting magazine and hopup setup, so a bit of work was done to get those parts to line up properly, but now that it’s powered by the PolarStar Fusion Engine, it brings the reliability of HPA powered gun to this WWII classic.