Heres the dope,
You can put a M16 bolt in an AR-15. If you also have the other parts to make your AR-15 fire full auto you HAVE an illegal AR-15 even if they are not in the gun.
If I own a silencer it doesnt have to be on the gun for the gun to be an illegally silenced weapon.
If I own enough parts to cause my AR-15 to go full auto, at anytime, that is an illegal weapon.
If I legally own 1 M16 and 1 AR-15, I can not own extra parts for the M16 since they can be used to convert the AR-15.
Simply having 1 M16 bolt, and 1 AR-15 isnt against the law. And I can install that 1 M16 bolt if I choose to.
If the Feds figure a way to cause the AR-15 to go full auto, INCLUDING dump firing, then I own an Illegal AR-15. Simply because I have a M16 bolt in it.
Yes I know you dont need an M16 Bolt to Bump fire, but they will use the Dump fire to satisfy the law statng you own a weapon that fires full auto.