Coming to an action movie near you …
Shooting starts at the 38-second mark and continues to the one minute, 24-second mark for a sustained burn time of 46 seconds. Depending on the rate of fire that could be as much as the stated 800 rounds but if that machine gun is running close to its standard cyclic rate of 750-800 RPM then it probably shot somewhere between 550 and 650 rounds, which is still kick-ass.
The only reason I question whether or not that was actually 800 rounds of belt-fed lovin’ is because it reminds me of the Ironman Pack Ammunition Pack System for Small Dismounted Teams, invented by then-Staff Sgt. Vincent Winkowski, winner of the 2010 Soldier Greatest Inventions Awards. That pack held 500.
Of course this could be an improved version of the Ironman Pack; it’s been a few years after all.
How many rounds did you count?