Many of the deadliest mass shootings in the U.S. have involved an assault-style rifle like the AR-15. WSJ’s Zusha Elinson reports on how Washington regulations have failed to stop the gun's rise to prominence.

Further Reading:America’s Failed Attempt to Ban Assault Weapons 

Further Listening: Red-Flag Laws, Their Application and One Mother’s Experience Learn more about your ad choices. Visit megaphone.fm/adchoices