It would be very easy to built a new post-ban lower into pre-ban configuration, but this would constitute the illegal manufacture of an "Assault Weapon" under the 1994 Krime Bill.

If you were caught with the rifle, it would be a simple matter of tracing the gun to the FFL who sold it to you.  The records would indicate the day you bought it, and it could be easily confirmed as being the first time the gun was sold.  It would also be a simple matter to check with the manufacturer to find out that the lower had been produced after the date.

Unless you got caught breaking some other law, it's very unlikely that anyone would care if you built your rifle up into pre-ban configuration.  However, the penalty is pretty harsh for those who ARE convicted.

-Troy

While everything you said is absolutely true, the problem is that, if things ever made it into court, it is up to the owner to prove the status of his AW.  You're betting that your argument would be enough to cast reasonable doubt.  I doubt that it would be enough, personally.  At best, it's a coin-toss.

Of course, the likelyhood of making it into court is pretty small, but the risks are large if it does happen.

-Troy