Colt Gov't Model AR-15 (pre-ban) would be ideal: as close as possible to the unquestionable standard USA militia/combat firearm without moving into NFA territory.
Would Seattle be good enough for you?
Perfect. Major high-profile city without the legal/practical obfuscations of D.C. or other cities currently suffering from terrorist attacks.
Whoever makes "the walk" must be absolutely clean: no criminal history whatsoever, no mental health issues, no questionable organization memberships, etc. His lawyer must know RKBA law inside-out, and know how to defend an innocent man.