nope. nope.

An upper receiver is just a part, like a bolt or a stock.

If you don't already have some paperwork to prove the status of your rifle, get it NOW, and hold onto it (Bushmaster can provide this for you [b]today[/b], but who knows about tomorrow?  Oly has had two fires, and all their records were destroyed.  Too bad for folks with no other documentation.)

Removing and selling your upper will not change your rifle's pre- or post-ban status.

-Troy