Outlaw firearms and only criminals will have them. This is every Christmas present and birthday present they ever got rolled into one for criminals. All you do is disarm their potential victims.
Oh, and if you're so sure a weapons ban would work - please tell me how that would be any different than Prohibition was, or the more current war on drugs, stopping illegal immigration, stopping drunk driving ... Because if there is some magic formula for making large federal programs anything but expensive failures then these other efforts need that same silver bullet.
In case you were wondering, Swift didn't really think the Irish poor should eat their children.