No matter which angle your gun is pointing, its surfaces are the same colour.
Have a look at this badly animated coin.

As it rotates, the face changes shade, becoming brighter as it gets closer to facing the light source.
Have a look at this badly drawn cube.

You can see the face furthest from the light source is darkest, but if you rotated it around a vertical axis it would get brighter. Try doing this to your gun. It should make it look more three dimensional and hopefully more like metal.
(But other than that it's a fine-looking gun!)