Americans have the highest rate of civilian gun ownership in the world, with an estimated 120 guns for every 100 people. In recent years, powerful weapons like the AR-15 have grown in popularity. Carolyn Presutti spoke with gun buyers in Tennessee about the sought-after semi-automatic weapons that are under scrutiny by gun-control advocates.Camera: Zach Wills, Roy Kim, Lynn Davis  Produced by: Adam Greenbaum   
 
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