Actionscript 3 :: Flash - Optimizing Collision Detection

I'm trying to make my first game in Actionscript 3. Its a simple artillery game where you have a gun at bottom left corner and AIs flying across the screen which you have to shoot down. Now, in a classing shooter game how this is achieved is either by firing a bullet from the gun and doing a hitTest of that bullet with the AI movieClip or by simply removing(or playing the death animation) the AI movieclip. But here's the problem. I dont wanna do either of them. I want to show a gun with a rapid fire rate and hence no bullets. And I also don't want the player to click exactly ON the AI movieclip to destroy them (just the gun/turret pointing at the correct direction should be enough). So here's what I tried. This image should help picture the whole thing.

Tried attaching a 'line' to the turret and checking for collision with AI clip. This obviously failed because of the bounding box problem when the line is slanting.
I tried putting multiple tiny movieClips ON the line and iterate through them in a loop and checking for any collision with the AI. This method partially worked, but it was too slow and didn't seem like the 'correct' method. I draw 2 hypothetical lines. One between p1 and p2 and other connecting p3 and p4 (please see the image above). p3----p4's lenght = AI.width and is a horizontal line running right through the center of the AI MovieClip. Upon mouseClick I check for any intersection between these two lines. Now if I have multiple AIs on the screen, Again i need to iterate through each of them, draw a fresh p3-----p4 and check for intersection with p1-----p2.

[Code]....