Just heard about this two days ago and am off to the range in another hour to try it out with my M4.
http://www.youtube.com/watch?v=GIC8SMttjjo
I'm afraid I can't spare the amount of ammo it would probably take to get as good as this guy is. But it looks very cool. I wonder if doing this will get earn me a visit from the BATF undercover thugs at the range. It's 100% legal, but I'm sure someone will want to check out the rifle.