The M1 Carbine, properly used, is nothing to trifle with. It's basically a rifle platform for firing a high powered pistol load.
Now, having said that, I think they were laying it on pretty thick showing a guy taking out a huge truck by nailing the driver with his Carbine.
You'd have to be a pretty darn accurate shooter to take out the driver with a single shot.
The purpose of the movie was obviously not only/merely instructional but inspirational. That's a nice way to put it.