Sound is a bit off for me. Everything seems to lack impact. Like the audio seems a little "naked". Character animation also looked a little floaty. But, I know how difficult 3D can be.
Edit: try adding some weight to your characters. Check out "the animators survival kit" it's a great book. For the audio, add some impact sounds. Bullets hitting metal, casings bouncing off the floor, so on. But it's a well done animation.