Originally Posted by Azathoth
The modified gun would have to be registered as a restricted weapon as I assume you would use a real lower receiver, and you could only ever bring it to a registered firing range and shoot it there. You would need be able to sell the weapon to anyone who doesn't have all the necessary carry ownership cards for the real gun. You would have to store the weapon as it's real
You're missing the point, read a little more closely.
The person would've already had to have the licence and registration for a real steel AR prior to such a conversion to airsoft, otherwise he wouldn't have the real steel AR. And unless the conversion to airsoft is one-way, there is no addition registration or reporting protocols to follow. He also said nothing about transferring it.