And to make things more confusing......... If it starts out (Born a pistol) it can always remain a pistol BUT if you ever attach a rifle upper at ANY time you can never switch back to a pistol again it is now a rifle forever? I know it's not very clear.
that's backwards, pistols can go back and forth between rifles and pistol but rifles have to stay rifles. this is how companies like mech tech and CAA can get away with selling their carbine conversions for glocks and thompson center can market pistol and rifle setups for their contender and encore lines.