I would support a buy back program, if and only IF, the very FIRST money spent was every penny of the private personal fortunes of every public and private citizen who voted for or expressed public approval for the program.
If it is SO important, let them put their personal money to the task, and spend taxpayer dollars ONLY when all their personal funds are gone!
In fact, I'll be generous...lets only take half of their personal fortunes of the supporters and all of the fortues of the sponsers, and make that the gun buy back fund. After all, these people are all rich, and we all know the rich aren't paying their fair share...(so we are constantly being told by these same rich people)
Let's confiscate only half of their personal fortunes (including spouses and immediate family members) and use that to buy guns with! I'd even allow them to write the confiscation off on their taxes, this year. Next year? well, if we haven't solved the gun violence problem by then, take ANOTHER half of their personal & family fortunes and try it again! And again the next year, if the job still isn't done!
But until, and unless this is done, I support no buyback program, nor the use of public funds in one, in principle or in practice.
After all, to be fair, if they can decide what we must do with our personal property, then we can decide what they must do with theirs!
The above is only partially meant in jest...
All else being equal (and it almost never is) bigger bullets tend to work better.