The ATF has banned armor piercing rounds specifically for that reason, but they also have a (17 page!) document listing how, when, and why certain armor piercing rounds fall under a “sporting exception”.
“Specifically, the definition of “armor piercing ammunition” in 18 U.S.C. 921(a)(17)(B) provides: (B) The term “armor piercing ammunition” means— (i) 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; or (ii) a full jacketed projectile larger than .22 caliber designed and intended for use in a handgun and whose jacket has a weight of more than 25 percent of the total weight of the projectile.”
It would appear the ban was intended to restrict the sale of what the press hysterically called “Cop Killer Bullets” back then. Phrase was all the rage. No mention of rifle rounds, only handgun rounds, and rifle rounds would later be explicitly allowed by the ATF:
“Between 1986 and 2011, ATF received few exemption requests for armor piercing ammunition. In 1986, ATF exempted 5.56 mm (.223) SS109 and M855 “green tip” ammunition containing a steel core. Similarly, in 1992, ATF exempted .30-06 M2AP cartridges. Since 2011, however, ATF has received approximately 30 exemption requests for armor piercing ammunition. Several developments since 1992 have spurred the influx of exemption requests.
Oh, man, I had TOTALLY not considered that angle. Yeah, as states ban lead ammunition, that’s going to spur development of alternatives which would ordinarily fall under the armor piercing definition unless they are granted a sporting exception.
I wonder if the “straight wall” ammo requirements had a similar impact?