A firearm is capable of burst and/or fully-automatic modes of fire (machine gun).
Yes, so long as the lower receiver was manufactured and registered before May of 1986.
Not from POF-USA. The Firearm Owners’ Protection Act (FOPA) prohibits individuals from purchasing Select Fire weapons manufactured after May 19th, 1986. Since POF-USA was founded in 2002, no POF-USA manufactured rifle or lower receiver falls into this category.
