The estimated number of guns in circulation in the United States as of 2009, according to a survey from the National Institute of Justice. That number includes 114 million handguns, 110 million rifles, and 82 million shotguns. The number of available guns has increased 62 percent since 1994, when there were about 192 million firearms in circulation. "Per capita, the civilian gun stock has roughly doubled since 1968, from one gun per every two persons to one gun per person," according to a report from Congressional Research Service .

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A collection of class room-safe training pistols are on display as students take a concealed weapons permit class at Take Aim Gun Range in Sarasota, Fla., December 15, 2012. As of 2009, there were an estimated 310 million firearms in circulation in the United States.