They are the stuff of legend, wielded by hit men and by James Bond. For decades, buying a silencer for a firearm has been as difficult as buying a machine gun, requiring a background check that can take close to a year. Now, emboldened by the election of Donald Trump as president, the industry has renewed a push in Congress to ease those restrictions, arguing that it’ll help preserve the hearing of gun users. “We look at this as a Second Amendment issue. We look at it as a health issue,” said Erich Pratt, executive director of Gun Owners of...