The U.S. Court of Appeals for the Fourth Circuit on Thursday dismissed a challenge to the federal ban on bump stocks, which are designed to help make semi-automatic firearms behave more like fully automatic ones. When attached to a semi-automatic firearm, a bump stock uses the weapon’s recoil energy after a shot is fired to “bump” the trigger back and forth against the shooter’s stationary finger, increasing the rate of fire. In October 2017, a gunman using semiautomatic rifles with bump stocks killed 58 people in Las Vegas, prompting the Trump administration to impose the following year a ban on those devices. Specifically, the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) reinterpreted the term “machinegun,” so that a 1986 ban on parts used to convert an otherwise legal firearm into an illegal machinegun now also covers bump stocks and attachments alike. The move effectively prohibits individuals from owning or …