It would appear the ATFs approval of the AR pistol in the first place is the root cause they are seeking to "correct." Expect a ruling on buffer tube status shortly, I say. I've said it before; this all about the AR15. Period. That rifle is our Capital Ship; it must be defended.
No truer words have been spoken, as much as don't like the AR (and don't even currently own one) it is in fact currently the most popular rifle in the US, and it is the one they have set out to destroy. Partly because it makes an easy target to the undecided, it can be presented as an evil black rifle with no good purpose other than mass shooting to the uninformed fence walkers that have yet to fall on either side.
They believe the average AR owner, owns 15 of them and that's why they sell so many, and that's why they believe they can portray AR owners as wack job domestic terrorist. That will also be their downfall, they are underestimating the masses.
If they can take down the the AR they can (and will) eventually get the rest. The opposite is also true, because the AR can be and is being so easily manipulated into being the ultimate "evil" rifle, if they can't take it down they want get any others. It really is the hill we MUST defend.
The best thing I can do for my right to a hunting rifle, a shotgun, and even a black powder revolver is stand and fight for the AR15, a gun I don't really even like.
And the ATF director is an idiot, any bullet fired at any officer is obviously a danger, but the bigger danger it the criminal behind it. They somehow don't want to talk about them, and our 75% recidivism rate, there in lies the problem.