Corrected entry: No way Kersey leaves the gun shop same day with a full auto AR-15. It would take boatloads of paperwork, waiting, and registration with the federal government. He could have bought a conventional semi-auto AR-15 much more easily.
Join the mailing list
Separate from membership, this is to get updates about mistakes in recent releases. Addresses are not passed on to any third party, and are used solely for direct communication from this site. You can unsubscribe at any time.
Check out the mistake & trivia books, on Kindle and in paperback.
Correction: There is no such thing as a full auto AR-15 unless someone has changed the firing mechanism in the lower receiver. You can not buy a full auto AR-15.
Kersey didn't even know how to shoot a pistol and had to practice with the throw down gun. The gun shop sold him the AR-15 capable of full auto. He would not know how to convert it.
Cinderdan
You don't need to know how to shoot to do a full-auto conversion. There are kits available with instructions online. A bump stock could also be easily added to the firearm to make it functionally full-auto even if it technically is not.
BaconIsMyBFF
Bumpstocks are a terrible gimmick that make firing and aiming properly very difficult. They are nothing more than a toy.
The gun store couldn't sell him a full auto AR because they don't exist, as the OP stated. There are military versions, like the M4 carbine which can be had as NFA items, but not in Chicago.