I can't believe anyone (other than elkman) would object to the following:
Ban all conversion kits- make it a federal crime with a minimum of 5 years in prison for the first offense for possession - 10 years for production or sales
Ban all magazines/drums over 15 rounds -same penalties as above
Still 90% would agree with these:
100% background checks on every sale, gift or transfer of a gun, rifle or anything that shoots a projectile. If you don't, then you are liable.
100% background checks at gun shows - there's nothing in the Constitution about how or where you buy a gun
Make manufacturers produce weapons that aren't easily convertible. If they refuse, write a statute that makes them liable for all damages those weapons create. Every other product is liable for such design issues. There's no excuse to create a loophole for guns.