there a couple of option but first draw a design that you want. Because I know you can do something like animation with frame set let say in all the frame you have a magazine clip but on each frame is one bullet art less until at the end. so that you can do each time you shoot go to animation frame self.frame+1.
Or you can use some sort of a array pop / delete for that one. Most game uses an animation art with frame to show the magazine clip.
But again send us an art clip of what you want and perhaps we can figure it out.