M2 Machine Gun PolarStar Fusion Engine Conversion

IMG_2201The The M2 Machine Gun or Browning .50 Caliber Machine Gun is very large machine gun, and it’s extremely rare to see one as an airsoft gun. Tom DiQuattro wanted to have his M2 replica converted to a PolarStar Fusion Engine gun so he sent it out to see what could be done.

The M2 replica is massive. It’s almost 6′ long, and it weighs in at 36 lbs without the box mag. It was decided that real .50 cal ammo can would be used as the box mag for the gun, and with the box mag fully loaded, the weight of the gun tops 50 lbs!

IMG_2202The replica was made with a solid aluminum barrel. It was not bored out. I attempted several tries to bore the barrel using extra long drill bits, but I just managed to mangle up the barrel (lesson learned!), so I had to ship the barrel back to Tom where he had a friend with the right equipment properly bore out the barrel. The barrel is connected to the main body of the gun by large threads. This required that the hopup be able to fit through the front of the gun, so it can be inserted with the outer barrel, since a long 650mm inner barrel would be used with the gun.

IMG_2177A G&G/CA M14 hopup was used since it had a narrow profile and could fit through the front of the gun. To hold the hopup in place, and to provide a way for a BB feed tube to attach to the hopup. a 3D printed hopup block was created. The hopup block sandwiches the hopup and locks it in place, and also supports the front of the Fusion Engine. The rear of the Fusion Engine was held in place by another 3D printed bracket, which also supported the mini circuit board and MCU box mag circuit (which links the box mag to the trigger on the FCU).

The bottom of the gun was uncovered, so another 3D printed piece was created to close up the bottom of the receiver.

IMG_2168The trigger lever on the replica was simply a metal piece held in place with a pin, pushing against a spring. To have it work with the Fusion Engine, a hard stop was added to prevent the switch from hitting the buffer tube, and a micro switch was added so it would be activated when the trigger lever was pressed.

The .50 cal ammo can was modified to hold a MAG brand box mag. A large 3D printed feed bed was used to hold the box mag mechanism in place as well as feed the BBs down into the box mag. It has a giant capacity of about 19,000 bbs!

IMG_2173The M2 Fusion Engine conversion was a bit of a challenge (especially that solid barrel), but with the extensive use of 3D printed parts (the Makerbox Replicator 2X 3D printer has been a fantastic investment), it was able to be assembled in a very user friendly and maintainable way.

When hooked up to a large air source, high BB capacity, the M2 Fusion Engine gun will provide game changing firepower to any airsoft skirmish!

Happy Airsofting!

– Rudy

Here’s are some videos of the M2 assembly and disassembly procedure:


Here’s a sustained fire test video:

(more videos coming soon)