Not a bad first...
Not a bad first submission at all. To start with, I'll say that I see some pretty good potential here. I don't think it would be an overstatement to say that your animation skills are above par for a beginner.
My only issue with this flash, all things considered, is the "tempo" of which the action moves at. It just seems too slow! The gun fighting and the music seemed to fit well together, but it was a bit spoiled by the lethargic-ness of the animation. Try adding some quick movements in the fight scenes and fast camera changes and stuff like that to raise the intensity level a bit.
I liked the heavy choice in music, it fit the mood of the flash, for sure. I would try experimenting with a more music video oriented flash. Something with the same type of action, but more built around the music.
Overall, you've got a great foundation to build on with this. Not half bad for a first submission, keep it up!