While those involved in the gun industry (including some firearm fans and most regulators) were familiar with bump stocks, bump stocks did not enter the average person’s knowledge until they were used to help a gunman convert his semi-automatic weapon into a machine gun to kill multiple people at a concert in Las Vegas.   A bump stock is a part that uses the recoil of the gun to fire multiple shots without requiring further pulls on the trigger.

Federal law bans the ownership of machine guns.  The “definitions” part of this law defines a machine gun as “any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual 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.”

Prior to the Las Vegas mass shooting, the Bureau of Alcohol, Tobacco, and Firearms took the position that a bump stock did not meet this definition.  After the shooting, to head off pressure to amend the law to clearly cover bump stocks, the Donald Trump ATF issued regulatory guidance that a bump stock did meet this definition — namely that it was a part intended to use to convert a weapon so that it would “automatically [shoot] more than one shot . . . by a single function of the trigger.” Continue Reading...