M855/ss109

[Gman]

The AR-basedhandguns and rifles utilize the same magazines and share identical receivers. These AR-typehandguns were not commercially available when the armor piercing ammunition exemption wasgranted in 1986. To ensure consistency, upon final implementation of the sporting purposeframework outlined above, ATF must withdraw the exemptions for 5.56 mm “green tip”ammunition, including both the SS109 and M855 cartridges.7

The way I read it, because the ammunition can be used in both semi-auto handguns and rifles, the ATF has decided to vacate the previous exemption for rifles.

...and if you "care less", it means you still care.