Look at this chart. The 6th line from the top is the M16 bolt carrier. Note how many AR15 manufacturers include this in their semi automatic AR15 type rifles, two of which have them as an option. The ATF's position is that an M16 bolt carrier group in a semi automatic AR15 rifle will NOT cause the weapon to fire more than one shot with a single function or manipulation of the trigger. It never has and it never will. The parts that convert an AR16 to an M16 are in the FCG, not the BCG.
