And now the NRA is on board with more regulations on these.

The National Rifle Association has called for "additional regulations" on bump-stocks, a rapid fire device used by the Las Vegas massacre gunman.
The group said: "Devices designed to allow semi-automatic rifles to function like fully-automatic rifles should be subject to additional regulations."
Republicans have said they would consider banning the tool, despite years of resisting any gun control.
Lawmakers plan to hold hearings and consider a bill to outlaw the device.
The NRA called on Thursday for federal regulators to review the legality of bump-stocks.
http://www.bbc.com/news/world-us-canada-41519815