I'm totally down with quantitative change, thanks. Your argument presupposes that there's no spectrum of violence and no gradient of difficulty. Gas attacks are extremely rare, despite the methodology for committing one being easily-learned and the materials necessary being simple to acquire. Fertilizer bombs aren't difficult to make yet the Columbine killers failed. Any kid that has ever leafed through The Anarchist Cookbook has fantasized about mass destruction via innovative materials but none- zero, zilch, nada - have succeeded. On the other hand, any chucklehead with a pulse can pick up a gun somewhere in these United States and ammo is the simplest thing to procure. Somehow, this always becomes a "yes guns/no guns" discussion without recognizing that neither the problem nor the solution is likely to be binary.