Whether a combination of parts designed or intended for use as a bomb can qualify as a 'destructive device'

QUESTION PRESENTED Whether a combination of parts designed or intended for use as a bomb can qualify as a “destructive device” under 18 U.S.C. § 921(a)(4) and 26 U.S.C. § 5845(f), and hence a firearm under 18 U.S.C. § 922(g)(1) and an unregistered firearm under 26 U.S.C. § 5861(d), when the defendant lacks one of the parts necessary to render the device functional. i