I saw a show just the other day where someone ran out of ammo with a 1911. The slide was locked back and they kept pulling the trigger. Click, click, click, about 6 times.
Actually, thats pretty realistic. Adreneline is a strange thing. Studies have shown that many civil war soldiers loaded several rounds without firing. Same was true in WWI and WWII, only there it was just failure to reload, one dead soldier and lots of clips. Pulling the trigger effectively while thinking "Gee, I should change mags" happens only through practice and mental preparadness. Sad but true.
FQ13 who practices a lot as he know what a bone head he can be when bleeding, scared and in pain. Never underestimate muscle memory and ingrained drills. The corralary to this is don't think, "Gee I know this stuff, it's cave man simple". Wrong answer. If you have to think about it, you won't do it.