I've been looking into them too.
Since I found out I need a new portion of my roof and that is taking money away from a car I was going to look at, why not put some money towards a gun? I also don't mind the 9mm round. Alot cheaper to shoot. I'm no sort of military with no AR experience so the 9mm route intrigues me.
Good looking RRA above. Do you mind listing what model it is, and what you have done to it? Or you can PM me.