Bureaucracy and non-lead ammunition
The pitch for "nontoxic," i.e., non-lead ammunition has long been at odds with the pitch to ban "armor-piercing" ammunition. Under Federal law, AP ammo includes any ammo with "a projectile or projectile core which may be used in a handgun and which is constructed entirely (excluding the presence of traces of other substances) from one or a combination of tungsten alloys, steel, iron, brass, bronze, beryllium copper, or depleted uranium." 18 U.S.C. §921(a)(17). In short, all bullets made of any likely useful metal OTHER than lead. The definition does have some exceptions, including "a projectile which the Attorney General finds is primarily intended to be used for sporting purposes."
Here's some video from Attorney General Lynch testifying in House hearings, in which Rep. Ratcliff points out that ammo manufacturers have sent in 32 requests for exemption over the past four years, and so far none has been acted upon, or even gotten a responsive letter. (Ms. Lynch responds that she has never heard of the requests). Odds are pretty good that it's the same today. Somewhere there is a letter delegating the AG's power to someone else, and that someone else could care less, nor does the AG.