Honestly, I really don't see how the ATF has a leg to stand on with this one. From the link in the OP:
Now, the core of M855/SS109 ammo does contain steel, but it is not composed entirely of steel as specified in the law and it does not contain tungsten, iron, brass, bronze, beryllium copper, or uranium. It seems to me that the ATF is trying to say that the law prohibits ammunition with any steel in it's core but, fortunately, the law is actually fairly specific about what constitutes an "armor piercing bullet" (specificity seems to be something of a rarity in federal gun laws). As anyone who has ever seen a cross section of an M855 bullet (and there's lots of pictures online) can tell you, a good portion of the bullets core is lead (about half) and the steel penetrator is basically a steel cone sitting on top of the lead core. Because of this, I really don't see how it could meet the definition that 18 U.S.C. 921(a)(17)(B) specifies.
Honestly, I think that the degree of specificity outlined in the law makes the ban on 7N6 ammo pretty questionable. However, I suspect the argument there is that the lead inlay around the steel penetrator is thin enough that it's considered an inner jacket rather than part of the core. I also note that the ratio of steel to lead in 7N6 is much greater than in M855. Regardless, the construction of M855 is different enough from 7N6 to eliminate these vagarities.
Honestly, the fact that the ATF ever issued an "exemption" for M855 is something of a red herring. M855/SS109 is not and never was "armor piercing ammunition" per the letter of the law. The fact that the ATF even considered "interpreting" it as such strikes me as a blatant attempt to see just how far they can over step their bounds before anyone does something about it.
emphasis addedSpecifically, 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.
Now, the core of M855/SS109 ammo does contain steel, but it is not composed entirely of steel as specified in the law and it does not contain tungsten, iron, brass, bronze, beryllium copper, or uranium. It seems to me that the ATF is trying to say that the law prohibits ammunition with any steel in it's core but, fortunately, the law is actually fairly specific about what constitutes an "armor piercing bullet" (specificity seems to be something of a rarity in federal gun laws). As anyone who has ever seen a cross section of an M855 bullet (and there's lots of pictures online) can tell you, a good portion of the bullets core is lead (about half) and the steel penetrator is basically a steel cone sitting on top of the lead core. Because of this, I really don't see how it could meet the definition that 18 U.S.C. 921(a)(17)(B) specifies.
Honestly, I think that the degree of specificity outlined in the law makes the ban on 7N6 ammo pretty questionable. However, I suspect the argument there is that the lead inlay around the steel penetrator is thin enough that it's considered an inner jacket rather than part of the core. I also note that the ratio of steel to lead in 7N6 is much greater than in M855. Regardless, the construction of M855 is different enough from 7N6 to eliminate these vagarities.
Honestly, the fact that the ATF ever issued an "exemption" for M855 is something of a red herring. M855/SS109 is not and never was "armor piercing ammunition" per the letter of the law. The fact that the ATF even considered "interpreting" it as such strikes me as a blatant attempt to see just how far they can over step their bounds before anyone does something about it.