I discovered this after unfortunately finding myself on the periphery of a very heavy fire fight in Baghdad in 2006 as an unarmed contractor without my body armor handy. A co-worker and I headed for cover about 500 ft. behind a wall to wait it out when BAM a bullet penetrated the wall in front of us, flew past us and struck a wall next to our heads.
I remember this clearly because as soon as the bullet broke through the wall everything went super slow-mo. I mean, like 10,000 frames per second Slow-mo (http://www.youtube.com/watch?v=jt6eyDYeJr0). The bullet had obviously slowed down and had started tumbling because it sounded like the most pissed-off bee as it headed our way. More interestingly, and without any control of my body, my eyes immediately went into tracking mode and I was able to follow the bullet all the way across the space we were in -- about 500 ft. I honestly have no idea how long it took to travel that distance, but it felt like a full 10 minutes even though it couldn't have been more than a fraction of a second.
The overwhelming memory though was how my body felt like it was stuck in molasses as my brain desperately tried to tell me to hit the deck and I simply couldn't move as fast as my brain seemed to be working. I remember being absolutely frustrated with this little fact.
As soon as the round hit the wall with an appropriate ping! sound, time went back to normal and the adrenaline hit like a rocket and we high tailed it out of there to better cover.
I also remember just being mentally tired the rest of the day after that. Could have been the adrenaline rush but I think it's from the slow-mo effect.