Assuming you take the stance that Guns Are The Problem, and you want to reduce the number of guns out in the wild in America, there is a very large problem that needs to be addressed: What about the 200 million guns currently out there in private hands?
Asking people to voluntarily turn in their guns is basically pointless. People paid money for their guns, and giving them away for free because someone else is scared of them, just isn't gonna fly. (You might as well ask people to turn their car over for free to save the environment. It's a fine idea, but it just isn't gonna happen.)
You can't confiscate privately owned guns by force because... well, that just ain't gonna work. Having the military, national guard, or whoever, come up to a house, knock on the door, and then search for weapons is only going to end up with shots being fired. Many of them.
So what you need is an incentive for people to give up their guns voluntarily.
Spitballing an idea here, but what if you got 80% of the retail value of your weapon as a credit with the IRS? Turn in $10k worth of guns, and you don't pay another dollar in taxes until your $8k tax credit is depleted, no matter how many years it takes to zero out your credit.
This has the benefit that the majority of gun owners are probably fairly right-of-center, and have the usual right-of-center abhorrence for taxes.
This does not get rid of all the guns, by any stretch.
But what it does do is get rid of the guns people don't really care about. The ones they don't have an attachment to. Or the ones they don't secure as well as granddad's old 12 gauge over-under.
So you have pulled a bunch of weapons from the market and melted them down, or recycled the parts, or whatever. The other guns are probably better secured and less likely to be pulled out from under mom and dad's bed, like the Sandy Hook shooter did.
If our goal is to reduce the number of guns available to loonies today - in addition to stricter background checks and waiting periods and sales rules - what kind of incentive to turn over a gun, would a gun owner respond to?
(I am a gun owner, so I am asking this question of myself, as well as this incredibly intelligent, polite, and thoughtful Hubski community... because there sure ain't any other site on the net where one could discuss this topic rationally and politely.)