IIRC according to my last CCW instructor, the accuracy rate among LEO's under duress (in a gunfight, for example) is 2 out of 10 rounds. Now I know statistics are fraught with problems, but *still*... LEO's usually have lots more training than citizens when it comes to taking down a bad guy.

Ever had buck fever? The shakes? The buck isn't out to kill you. In a gunfight, the bad guy is. I've been in one gun confrontation and my brain just went on autopilot. I forgot to take the safety off the shotgun even though I practiced it over and over. Luckily the perp that was on the other side of the door was unarmed. This is why a DAO is such a good option. (BTW, the racking of the shell with the slide didn't phase the perp in the slightest...he was so stoned I don't think he even knew what the sound was)

So, missing six rounds is not unthinkable and may not indicate that one's aim sucks.