Mayors Against Illegal Guns, the pro-regulation group cofounded by Bloomberg LP founder Michael R. Bloomberg, is at it again. In addition to lobbying, the group has been systematically producing information, which is kryptonite to the National Rifle Association.

In a map released today, the mayors show that more than 98 percent of Americans live within 10 miles of a gun dealer. How can that be? Because there are 58,344 federally licensed gun dealers -- about four times the number of McDonald's -- in the U.S. That's right, it's easier find a Smith & Wesson than to locate a Big Mac.

The map pretty much destroys the NRA's contention that background checks of private gun sales would constitute a horrid inconvenience. Instead, the overwhelming majority of sellers and buyers could travel less than 10 miles to a registered dealer, where an instant background check could be conducted.

The map bolsters the case of Democratic Senator Charles Schumer of New York and other supporters of universal background checks. Whether it influences NRA senators is another matter. In other news this week, the NRA announced its opposition to legislation to retrieve guns from felons and the mentally ill who are legally barred from owning them.

(Francis Wilkinson is a member of the Bloomberg View editorial board. Follow him on Twitter.)