Find out all about it in this video as posted by Fulcrum himself... "Yes, this is exactly what it looks like. The folks at Commando Elite Paintball asked me to turn their Browning .50 HMG model into a fully-functioning airsoft 50 calibre machine gun.  And it's not as complex or expensive as you may think...

The Browning replica has a lot of internal space, downside is it's welded and riveted together. So anything that is to be fitted inside has to be assembled inside the .50 cal. Commando Elite gave me an old Valken rental M4 to chop up and stuff inside the HMG. And to keep things simple and low stress, we're going to do another cheap HPA build.

Now HPA and 'Cheap' are two words that usually aren't compatible. But using a homemade ECU, printed engine and pneumatic parts found on Amazon you can create a HPA engine for an incredibly low price. And compared to reshimming an AEG gearbox and the cost of a decent gearset, plus the failure mode of AEG gearboxes usually being more damaging. A cheap, homebrew HPA system is a much more sensible solution."