Take a hard look at history, namely Prohibition. What happens when you restrict access to a resource in demand? People find new, illegal, and potentially more dangerous ways to sell it.
Let's disperse with the idealism that regulating/destroying guns will somehow create world peace. It will create new opportunities for criminal-entrepreneurs. Black markets. Increased crime. More guns in the hands of criminals, and less in the hands of honest people (I don't particularly care about how many "honest" people have guns, but I do care about the consequences of over-regulation).