The Feds went berserk over the issue regarding Thompson Center Contender and Contender firearms being convertable back and forth between long and handgun. But the courts ruled that the fact that they could be converted back and forth between Handgun and long gun did not violate any laws and was upheld. In PA where I live the way to go forward is to buy the firearm as a handgun( more restrictive in terms of law) and then get the goods to convert to a long gun. Your state may vary.
