If you really want to learn to shoot an AR with iron sights, buy this book, $6.95 from the CMP, written by the AMU, best shooters in the world:
https://estore.odcmp.com/store/catal...4=¬e5=&max=
If you want to learn to shoot from barricades, get this DVD, also $6.95 put out by the same people CMP/AMU
https://estore.odcmp.com/store/catal...4=¬e5=&max=
You want the muzzle extended past the barricade, if not the muzzle blast is gonna disturb you big time. If you're shooting from barrels, (as in some matches) do not stick the barrel in the barrel, back up a bit, again the muzzle blast will interfere.