AR57

I just found this while surfing for info on setting up the TT 2-Piece MAV (one of which I should have by the middle of the week). I ran across the Weapon Evolution forum which looks pretty good in itself, and on it was a link to this site about the AR57, an AR15 upper receiver which accepts P90 magazines. There's a few videos of it in use on YouTube, one of which is below.