07-30-2011, 05:03 PM
To carry DirectDrive's explanation one step further....there have been legal cases where people have had more than just a M16 carrier in an AR15. It has been established that the carrier by itself is considered legal, but if you have a safety selector from a M16 in the same gun with the carrier, thing could start to get interesting even though you still do not have a machine gun. There are many surplus safety selectors that are available in surplus parts kits. It is best to make sure that you have a semi-auto commercial selector before you put your AR15 together.
Be safe so you can go shooting another day
Be safe so you can go shooting another day