It seems Philadelphia got some federal grant money -- nearly a cool million -- in order to run some gun buyback programs. They did run the programs, but over half of the money they got went to corruption rather than legitimate expenses, including an unofficial raise for the program director, $28K in missing gift cards that were not traded for a gun, $40K in rental for a building to operate in for only a month. The program did collect almost three thousand guns, but at a cost of nearly $300 each (only $100 of which was the gift card they gave to the person turning in the gun).
I suspect that these programs are basically money laundering for campaign expenses anyway.