I’ve seen boonie grass and that background looks like it. Further the author says “look at the muzzle brake” - you can’t see the muzzle break because it has a plastic/nylon cap cover on it! I have a bunch of those for my ARs.
That said, it was dumb to be fiddling with the sling even if there was no magazine in it. The gear? I have no idea what the journalist hooch had in the way of bush gear, but I bet it wasn’t much.
The correct term is “muzzle brake”. It brakes or retards recoil by redirecting muzzle gases.
For Al’s rifle, from Wikipedia, “...the U.S. military declared the A2 flash suppressor as a compensator or a muzzle brake; but it is more commonly known as the “GI” or “A2” flash suppressor.”