Better build that 80% receiver now!!

[RocketScientist]

(1) A firearm receiver casting or firearm receiver blank that--

(A) at the point of sale does not meet the definition of a firearm in section 921(a) of title 18, United States Code; and

(B) after purchase by a consumer, can be completed by the consumer to the point at which it functions as a firearm frame or receiver for a semiautomatic assault weapon or machinegun.

There is no way this law would be enforceable, as literally anything would meet this definition. A simple block of steel (A) does not meet the definition of a firearm and (B) can be "completed by the consumer" (ie machined) to the point it will function as a firearm frame or reciever for a semi-auto weapon.

Hell, a large enough block of wood can be cut into a workable firearm frame. Polystyrene pellets can be 3-d printed into a gun.

As-written, this law basically bans the sale of raw materials, as pretty much anything can be turned into a gun by a consumer. Just go to improguns if you doubt this.