Well, reasonably speaking, the *difference* is between 20-30 and 300, not between 20-30 and 12. The first big result is that the car was not hit by a hell of a fire. Simply some second of fire from a single automatic rifle. Not counting shots that have missed, of course.
BTW, "Week End Warriors" reservists of First Battalion, 69th Infantry, are not famous for their training at all. The journalist have been very lucky, IMO.