Not necessarily. The rate of fire is far more consistent than you normally get with a bump stock. Converting any given gun to full auto illegally isn’t that hard, it can even be done with a shoelace. During the course of the investigation the ATF was prohibited from testing or inspecting any of the weapons and they admitted that they do not know if they were illegal machine guns or not. All it would have taken is a pair of tin snips and a sheet of mild steel from home depot; the asshole more than proved that he had time and ability to do so.