It just seemed right to place the gun on the arm. Less goofy than on the shoulder. How are you supposed to aim a gun attached to your shoulder anyway? With your torso? Twist and shoot...
Nice positioning, great usage of the weapon.. exactly! Why the hell should he have it on his shoulder? When painting white it's hard to get any highlights as your already working with the brightest colour possible... so.. I'll give it a 9! Maybe more freehand could make some people like it more? People are harsh...