NOTICE OF PUBLISHING ERROR
On Feb. 13, 2015, ATF released for public comment a proposed framework to guide its determination on what ammunition is "primarily intended for sporting purposes" for purposes of granting exemptions to the Gun Control Act’s prohibition on armor piecing ammunition. The posted framework is only a proposal, posted for the purpose of receiving public comment, and no final determinations have been made.

Media reports have noted that the 2014 ATF Regulation Guide published online does not contain a listing of the exemptions for armor piercing ammunition, and conclude that the absence of this listing indicates these exemptions have been rescinded. This is not the case.

Full text here.  (edited to fix link)