This ammo was never intended to be AP. The steel core was simply a cost savings method. The ATFB is the only entity that classifies steel core as AP. While the core is not tungsten or hardened steel, it may penetrate some lower grades of bullet resistant vest - especially the earlier ones. since the steel core is harder than lead, it purportedly will not deform and get grabbed by vest fibers. I have shot steel core at mild steel plates and the core bounced back and hit me in the foot. When shot with lead core, it penetrated clean through. So, not Armor Piercing, just cheap bullet resistant vest piercing. The ammo was cheap back then, but lead core was only slightly more expensive. Still can find it for sale every once in a while. A few months ago, I bought an ammo can with 600 rounds of it for a whopping $23.00