It doesn't seek out a specific angle, or really stabilize that much. I've been using this glitch to make monowheels a long time, although if you make an opposing device of equal power it does stabilize fairly well.
I'd seriously suggest adding the circles to the box with CSG so you just have one geometry. Complex object spawning is... complex. And either way I can't think of a good way to set the angle of the object relative to the gun firing it, so if you want it to work you're going to have to make the gun only fire in one direction or do some complicated math and onCollide sensors.
But to just make something spawn at the collision point, you would use the following to define its position.
pos := e.pos;
e. stands for event, I think. It has a position, but nothing else as far as I can tell.
If standardtoaster's scene isn't quite what you're looking for, this would not be my first scripted gun. Just some questions:
I assume you want it to be automatic?
Is it only going to fire at one angle, or do you want it to be aimable?
How fast is it going to have to move without failing?