Ah, thats why you didn't.
The belt is misunderstood. The actual barrel is the only part intended to swivle, the base of the barrel is meant to be a sphere of metal you could say.
I decided to do it this way, because of the belt, since it would look horrendous whenever the turret moved up or down. The black bit under the main turret is intended for the turret to rock up and down, rather then rotate. The entire piece is meant to look similar to a bunker turret (think D-Day, from the german side) A single, strong turret with major front armor to defend a single location. That is anyhoo, the intention.
(If anyone takes me up on it, I am working on the sprite more, so if they ask, i will PM them the new version.)