Multiple _visible = false; - possible to simplify?

Hi,

I have 20 bullet_mc that are _visible = false; and when users click a button which is over the invisible bullet_mc, that particular bullet_mc becomes visible. That all works but I would like to simplify the code if possible. This is what I’m using now:

Frame:

_root.bullet1_mc._visible = false;
_root.bullet2_mc._visible = false;
_root.bullet3_mc._visible = false;
_root.bullet4_mc._visible = false;
//etc etc

Button which is on top of bullet_mc:

on (press){
    _root.bullet1_mc._visible = true;
}

on (rollOver){
    _root.bullet1_mc._visible = false;
}

How can I make this easier to use?