A ban on dozens of semi-automatic rifles cleared the Washington state Legislature on Wednesday and the governor is expected to sign it into law. The high-powered firearms — once banned nationwide — are now the weapon of choice among young men responsible for most of the country’s devastating mass shootings. The ban comes after multiple failed attempts in the state’s Legislature, and amid the most mass shootings during the first 100 days of a calendar year since 2009. The Washington law would block the sale, distribution, manufacture and importation of more than 50 gun models, including AR-15s, AK-47s and similar...