http://www.youtube.com/watch?v=11fcg543Jow&feature=youtube_gdata_player
Reminds me of this. I think some of the NFA rules make sense (on pistols like this) on an AR "pistol" notsomuch.
Somebody really needed to teach him a good fighting pistol grip. It looks like he was shooting 90% strong hand, 10% weak. I really don't see how you could allow your weak hand to disconnect from the pistol like that.