I'm not a lawyer, blah blah blah....
The sense I get is that if you have evil parts in your posession, without a complete evil rifle, they consider that an attempt to build a new evil rifle.
If you already have an evil rifle, then you have an evil rifle, and spare evil parts.
If you have evil parts, but no reciever with which the evil parts can make a whole rifle, you simply have a pile of evil parts.
Scenario, which I think works: I've got a gunbuddy who owns 0 parts associated with either the AR series, or the M1A series. I own nothing associated with the FNFAL or cetme. Presumably, we can buy evil parts for each other, and throw a swap party when the damned AWB expires, because until we swap, neither of us can build a whole evil rifle.
Now, the interesting question is whether Agent Schmuckatelli might consider this to be some sort of conspiracy thing. It could be alleged that such a scheme might be considered a conspiracy to break the law, when in fact it is a conspiracy to OBEY the law.