Most likely some type of trigger finger or something to trick the controller that it's trigger is being consistently squeezed faster than normally possible., I'm not much of an expert in these circumstances and don't exactly know how it was done. But I am a gun collector, there isn't a legit way to make that gun fire at that rpm. I have multiple full auto pdx 45s and hawksaws. Plus it was the vender roll which was shown in the video.