[Geoff Winnington-Ball (RIP)]

If you look closer, you'll note that although it's an air-cooled barrel, the gun still retains the standard M2HB barrel jacket. I suggest that this gun has indeed been scrounged, although it started out as the slower-firing M2HB... spare barrels were likely scrounged out of a crash-landed fighter! Easier to carry and lighter to handle... all the same, the vibration from that thing must have shaken the piss out of everyone onboard, never mind the noise!