Found this:
(21) The term “engaged in the business” means—
(B) as applied to a manufacturer of ammunition, a person who devotes time, attention, and labor to manufacturing ammunition as a regular course of trade or business with the principal objective of livelihood and profit through the sale or distribution of the ammunition manufactured;
(22) The term “with the principal objective of livelihood and profit” means that the intent underlying the sale or disposition of firearms is predominantly one of obtaining livelihood and pecuniary gain, as opposed to other intents, such as improving or liquidating a personal firearms collection: Provided, That proof of profit shall not be required as to a person who engages in the regular and repetitive purchase and disposition of firearms for criminal purposes or terrorism. For purposes of this paragraph, the term “terrorism” means activity, directed against United States persons, which—