New ruling from ATF:
http://www.atf.gov/regulations-rulings/rulings/atf-rulings/atf-ruling-2011-4.pdf
Reader's Digest version:
If you have a firearm that starts out as a pistol (or virgin receiver) and you possess parts to legally make it into a rifle OR a pistol, you are NOT in constructive possession of an SBR. You can switch it back and forth as long as you assemble it legally.
This sounds like it's basically a long-time-in-coming response to the United States vs. Thompson/Center case where SCOTUS ruled that having the parts to assemble an Encore rifle or pistol does not constitute constructive possession of an SBR.
http://www.atf.gov/regulations-rulings/rulings/atf-rulings/atf-ruling-2011-4.pdf
Reader's Digest version:
If you have a firearm that starts out as a pistol (or virgin receiver) and you possess parts to legally make it into a rifle OR a pistol, you are NOT in constructive possession of an SBR. You can switch it back and forth as long as you assemble it legally.
This sounds like it's basically a long-time-in-coming response to the United States vs. Thompson/Center case where SCOTUS ruled that having the parts to assemble an Encore rifle or pistol does not constitute constructive possession of an SBR.