Gun-control advocates have recently been throwing around an impressive new number. President Obama used it last Wednesday, claiming: “as many as 40 percent of guns are purchased without a background check.†Vice President Biden and everyone from the New York Times to the Wall Street Journal to USA Today repeatedly use it. That “fact†provided the principal support for his first announced gun-control proposal, “universal background checks.†But unless you include family inheritances and gifts as “purchases,†it is simply false.The Brady Act background checks currently prevent someone who buys from a federally licensed dealer from buying a gun...