According to the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), 9mm ammunition is classified as AP based on its construction:
: A full-jacketed, >.22 caliber projectile intended for handguns with a jacket weighing over 25% of the total projectile weight. 2. Civilian Purchase Restrictions buy armor piercing 9mm ammo
makes it illegal for civilians to purchase, import, or manufacture armor-piercing ammo. Ammunition Regulation - Giffords.org According to the Bureau of Alcohol, Tobacco, Firearms