Mayor Michael R. Bloomberg’s attacks on the gun industry are legion, and familiar far beyond the boundaries of the city he runs. They were heard again just hours after the shooting massacre in Aurora, Colo., in his calls for tightened gun control.

So it may come as a surprise to some that in June, New York City sold more than 28,000 pounds of the Police Department’s spent shell casings not to a scrap metal company, as it has in the past, but to a Georgia ammunition store. The store, Georgia Arms, routinely buys once-fired shell casings, reloads them with bullets and sells them to the public.

The store sells bags of 50 bullets, at about $15 each; per Georgia’s gun laws, no questions are asked and no identification or registration is required. It is a transaction that could not occur in New York City, where it is illegal to possess ammunition without a license to own a gun, and where obtaining a license to own a gun is harder than in most other states.

The sale of shell casings to Georgia Arms is perfectly legal and not uncommon; other police departments sell their used casings. And many of its “factory loaded” bullets, as the second-generation rounds are known, are sold in bulk to police agencies for use on their own firing ranges. They are less expensive than new ammunition.