Monroville said:

Uhh, but the gun is recoiling. If the gun was moving into position, the gun barrel wouldn't be snapping back the same way it does when you see it actually shoot. In fact, wouldn't the entire ball turret be moving if it was prepping for a shot?

it isn't recoiling. The gun is coming out from inside the ball and the ball is moving into place. In the firing shot earlier in the movie you can see that the gun comes from inside the ball before it takes it's first shot. Like i said all this is clear when you see the whole sequence