The law on armor piercing projectiles has absolutely nothing to do with a projectile’s ability to pierce armor. It is ONLY defined in terms of its composition. Has a steel “core”? Yes? then it is, by definition in law, armor piercing.
The Federal Statute - "Armor-piercing ammunition is defined as any projectile or projectile core that may be used in a handgun and that is constructed ENTIRELY from one or a combination of tungsten alloys, steel, iron, brass, bronze, beryllium copper, or depleted uranium."
ATF's decrees have not followed or is consistent with the law. They've been bullying manufacturers and sellers, and it's easier for the commercial sellers who've believed to drop the cartridges than call them on their bluffs.
It's the reason why the ATF doesn't charged anyone because it's not the law, unless it is made 100% of the hard metals listed in the law.
The word "entirely" means 100%, all, and completely made of those metals listed in the federal statute, and not 20% or 30% or 60% off - no the law says 100% as "entirely" constructed of those materials or "entirely" a combination of them.