I think you will find that was filmed at the Dillon range. A rather innovative man named Dillon invented a progressive reloading system for folks that reload their own ammunition and has made a pot full of money. His hobby is machineguns of all kinds....to include mini-guns and quad fifties amongst the collection. He also flys a fixed wing airplane with guns and does strafing runs at his private shooting range.
One does have to admit the old mini-gun puts on a show.....but I would imagine a gatling style .50 caliber would be even more impressive from a Huey.
Ah, the smell of burnt powder....and the rattle of empty casings rolling around the cabin floor!
How many guys ever have the door gunner dump hot brass down your collar while shooting out the cabin door?