If you want to be taken as something more than another raving leftist lunatic, check your facts. That 40% figure has been panned. Even Joe "gun-safety" Biden admitted the number quoted by Barack "Liar in Chief" Obama was erroneous.
But mostly -- drop the pretense that any supply side action does any good to prevent gun crimes. Point of sale restrictions only make it more difficult to acquire a weapon. Those intent on useing them for violence simply buy them on the black market. And those honest citizens who want them to defend themselves simply do without and get killed by illegally armed hooligans.
The ONLY practical, moral, Constitutional deterrent against gun violence is the belief that one's victim may be armed.