This photo, taken from a video posted on the Slide Fire website, shows the after-market bump stock device, which uses the gun's recoil to cause rapid discharge of bullets. (CNSNews.com) - On June 7, 2010 -- about a year and a half into the Barack Obama administration -- the Bureau of Alcohol, Tobacco, Firearms and Explosives issued an opinion letter, giving the go-ahead to an after-market accessory that allows the user to “bump fire” a semi-automatic rifle. A company called Slide Fire had earlier sent its patented replacement shoulder stock to ATF’s Firearms Technology Branch, asking for an evaluation of...