The Myth of Stormtroopers not being able to shoot?

Youngest has suddenly taken an interest in Star Wars after playing a game on line. I told her to start with episode IV. Watching it with her I noticed that the Stormtroopers in the boarding action at the beginning shot up the Rebel defenders pretty good. <div><br /></div><div>Perhaps there is something to them pulling their shots at other times intending to let the Rebels to think they got away with something?</div><div><br /></div><div>Or was it that the Stormtroopers in the boarding action had Vader breathing down their necks and thus were  well motivated. </div>