It's tough to know exactly how many guns we have in the United States. Most estimates of the number of guns in the U.S. use federal tallies of the firearms manufactured, imported and exported by U.S. gunmakers.
A 2012 Congressional Research Service report published exactly one month before the Sandy Hook school shooting put the number of civilian firearms at 242 million in 1996, 259 million in 2000, and 310 million as of 2009.
If that 310 million number is correct, it... [Washington Post, v...