FILE - In this Feb. 1, 2013, file photo, an employee of North Raleigh Guns demonstrates how a "bump" stock works at the Raleigh, N.C., shop. The gunman who unleashed hundreds of rounds of gunfire on a crowd of concertgoers in Las Vegas on Monday, Oct. 2, 2017, attached what is called a "bump-stock" to two of his weapons, in effect converting semiautomatic firearms into fully automatic ones. (AP Photo/Allen Breed, File)

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