You guys are all missing the problem with these buy-back programs!
#1 It actually increases crime in the area or at least provides a form of legal cover. One of the prerequisites for such a program is to assure the "criminals" that there will be no penalty or check in the transaction.
So why not pull a few heists or heck maybe knock off a competitor or two, maybe some local gang members on your turf THEN turn the evidence of the crime over to the cops who will make sure that evidence is either melted down or dumped in a very deep part of the Atlantic? Then you can take the legal revenue you made from the cops and buy some newer and "cleaner" street guns where you got the old ones?
#2 These buy-back programs are the forerunners of paid Confidential Informant programs at the mom & pop level.
We managed to get "assault weapons" banned but everybody knows somebody who's got one and you know, may not even realize they're in possession of deadly hardware. For $100 we can guarantee that your grandson will stay safe and not be arrested. We only want the gun. DO THE RIGHT THING!
I promise you that at first that is exactly what will happen, the guns will be taken with no action taken, except that instead of not keeping records, this time copious records will be kept for future use of both the informant and the one in possession. Later on, when "no knock" midnight searches become common, the former CI's will be blackmailed into giving up more names and the former possessors will be rounded up as possible "insurgents."
Think it's a fairy tale? Look at history (which I have taught for 19 years). This is world history from 1936 to the present.
We're just a little bit slow catching up. Don't let the wonderful results in Heller fool you, when a real TYRANT grabs power the USSC won't matter.