Lived in Memphis for about 10 years (moved away about 7 years ago) . . . Saw this maneuver in action personally a couple of times. Basically when crime gets so out of hand that even Memphis folks start getting riled about it, the corrupt local politicians in that city (Herenton, Ford(s), Peete, Bolton, etc.) stage a big gun turn in. About 20 - 40 ghetto firearms with doubtful ability to go bang get turned in for a gift card or cash worth way more than the gun. The pols slap each other on the back for the cameras, blow a lot of useless wind at TV microphones and go back to stealing themselves.
The City of Memphis is a dysfunctional cesspool. Almost 100 murders already this year which per-capita is probably more than places like Compton, Gary, IN, Detroit, South Bronx, etc. The police force is so corrupt and demoralized, they simply dont give a d*** anymore. Decent folks have left the city for the far suburbs long ago and all that's left is the very bottom of the socio-economic barrel and a few liberal "elites" who just love the "culture" of the place.
It's almost funny how the national media grabbed hold of this and styled it as if some bunch of enlightened southerners were giving up their evil guns for the common good. . . . barf!