He apparently had 8 different weapons, with mags/drums. He wasn’t firing controlled bursts because he was using it as an area weapon - firing from an elevated position into a crowd. For him, volume of fire was more important than accuracy. He had multiple weapons to prevent overheating/malfunctions from emptying mags/drums at the cyclic rate.
On reflection, this makes sense. If he knows he only has x minutes until cops kick down his door, then expend maximum number of rounds in shortest time. At 6-700 yards, given he is a hunter and has some shooting experience, he could control fire sufficiently to keep his shots in that box.