Need help with hitTest

I am just trying to learn on how the hittest works. I have attached the file that I have been playing with. Here is the code I am using:
on (press) {
on (release) {
//see if in center of target
onClipEvent (enterFrame) {
if (this._parent.target_mc.hitTest(this._x, this._y)) {
this._x = _parent.target_mc._x;
this._y = _parent.target_mc._y;
this._parent.target_mc._alpha = 50;

When i test the movie it works, but I do not want it to jump into the center of the target and also I would like it just be the front of the bullet_mc to
work with the hitTest not the center of it. THANKS