This is apparently the year of reclassification and reversals from the BATFE.  Previously allowed “green tips” are going to be banned as “armor piercing” by eliminating it’s exemption:
http://www.atf.gov/sites/default/files/assets/Library/Notices/atf_framework_for_determining_whether_certain_projectiles_are_primarily_intended_for_sporting_purposes.pdf

It appears as if the move is related to the “AR Pistol” variants as the language they are referencing is from the 1986 law:

(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.

The issue is that regular ball M855 is not “entirely” made of the listed materials–it is a steel tip over a lead core, so I think they are going after the angle of the steel tip weighing more than 25 percent of the entire round.  I believe the M855A1 jacket is about 33 percent of the weight, and the M855 Lead Free variant is a tungsten core.  I don’t know the weight breakdown of the regular ball, though.

The BATFE had previously granted an exception to the M855  (since they had declared it as armor piercing) for use under “sporting” purposes and it looks like they are going to remove this.

The BATFE is accepting comments until March 16th regarding this. Now lets be clear this is about a change in the law not politics. Now where did I put my phonebook?

You can read the release from the NRA-ILA site:
https://www.nraila.org/articles/20150213/batfe-to-ban-common-ar-15-ammo