It will be huge in the players hands and the top of the model is supposed to be flipped to the +Z Axis, Don't scale unless your in edit mode and if you already have select each section of the model in object mode, and press Ctrl+A and select (Scale and Rotation to ObData) to prevent lighting issues, More pictures would be helpful for animation, and Chapter 3 of
This teaches weapon animation, if you need any more help i will try and answer.
EDIT: Also you need a mountPoint, muzzlePoint, detail32, and Shape, the Tutorial above shows how to set these up in chapter 2.