WASHINGTON — Sell a rifle to a law officer, stop a crime. Trade a pistol for a McDonald's voucher, prevent a shooting. Atlanta bought 837 guns from residents last month, and Houston collected 779 earlier this month. Citizens sold 282 guns to authorities in Las Cruces, N.M., 754 in Baltimore, eight in Prichard, Ala., and 2,192 in the District of Columbia. "What's the value of a life saved?" asked Atlanta Mayor Bill Campbell. "We are going to do this again and again... (GunPolicy.org)