This looks like a lot of fun. I have seen videos of matches at Knob Creek and it seemed like a waste to use a machine gun. Shooting a semi auto would actually be more accurate and faster than using a machine gun. However some of the stage design in this video lend themselves to using machine guns as an advantage. Especially stage 2 where you need quite a few rounds on target to get the spinner to spin up and over. As well as the sled that you have to push with rounds on steel. That would take a lot longer with a semi auto.
The shooter is using an M11/9 with a Lage Max-11 upper, and a Bowers VERS-9s suppressor. The M11 looks to have a Cmore red dot.