When I try and unwrap your model I get a message appear in my toolbar:

And when looking at your object's dimensions, I see, as the previous message indicated, that you have non-uniform scale (not all values are '1'), meaning the object has been scaled in object mode:

You need to press Ctrl+A and choose Scale to 'apply' the scale that you did in object mode to the underlying vertices.

See Why is it important to apply transformation to an objects data? for more information.

When I try and unwrap your model a message appears in my toolbar:

And when looking at your object's dimensions, I see, as the previous message indicated, that your object has non-uniform scale (not all values are '1'), meaning the object has been scaled in object mode:

The unwrap operation works on the vertices, essentialy ignoring any scaling in object mode you have done to the object (as I understand it). You need to 'apply' the scaling you did in object mode, to the underlying vertices. You can do this by pressing Ctrl+A and choosing Scale.

See Why is it important to apply transformation to an objects data? for more information.