I'm not into banning anything because it justs makes people want the thing more. The key is in the wallet. Tax ammunition, heavily. Then only rich people will have guns! j/k. If you can price ammunition out of the range of most people who seem to enjoy using guns for nefarious purposes, then all they can do with their guns is throw them at you (well, I guess you could still be pistol-whipped). Of course, a black market will develop for cheap over-seas ammunition and this is where the low-lifes will buy their bullets, thus negating any positive effect of the tax except for placing a higher financial burden on the responsible gun owners. Though, you could hope that the cheap over-seas ammo will be of sub-standard quality and will blow up in the face of the user. Now that would be fun.