"Production of AR-style guns has soared since the federal ban expired. In 2004, 107,000 were made. In 2015, the number was 1.2 million, according to the National Shooting Sports Foundation (NSSF), an industry trade association.... Today, one of out of every five firearms purchased in this country is an AR-style rifle, according to a NSSF estimate. Americans now own an estimated 15 million AR-15s, gun groups say."