As a gun owner, I ask why don’t the authorities follow up on straw man prosecutions, follow up when a gun owner falls out of law abiding and must give them up, or let state laws (see Arizona) reduce ATF efforts?

The bump stock might be legal, but a plain language reading says really not.
I say this is a lack of prosecution by ATF. A fast track to jail is full auto conversion kits in the same room with a compatible gun. Anyone with experience in this area of the law, please chime in. I’m email Chuck Michel, an attorney famous or infamous if you like for this area of expertise.

Federal Definition of a Machine Gun
For purposes of federal law, a machine gun is defined as:

[A]ny weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manually reloading, by a single function of the trigger. The term shall also include the frame or receiver of any such weapon, any part designed and intended solely and exclusively, or combination of parts designed and intended, for use in converting a weapon into a machinegun, and any combination of parts from which a machinegun can be assembled if such parts are in the possession or under the control of a person.16

I’m about a half millimeter from calling bullshit on the legality, and shaming the authorities accordingly.