Shooting people with guns mechanics

Ok. Looks like i'll be looking into Phoenix Command and Unknown Armies (which i've briefly glanced at before, but which i know really nothing about). Eric, thanks for your post. Thanks to everyone else as well, but Eric brought up some interesting stuff and helped me mentally clarify what i want to do.

My current thinking is to do a couple of modifications to The Burning Wheel's combat system and see what happens. The Stell vs. Hesitation mechanic (with its subsequent loss of combat actions) may cover the recovering from surprise thing and combat scripting may well model the short timeframe for actions.

To address Mike's point on genre, i'm looking for something that is pretty realistic. I guess it's time to go check UA out.

If anyone else has brilliant ideas, or simple observations, they are welcome.

Thomas