Enforce a huge price increase and tax on bullets purchased by civilians. Less shots would be fired if each cost of $100

People will continue to get guns no matter how many laws are created. Guns are useless without bullets. If the bullets are very expensive for civilians to purchase then maybe less people would go on mass shooting sprees using guns that shoot multiple rounds.
A portion of the price increase could go toward defense spending, because what gun loving American doesn't love spending more on our national defense.
I think that it would also be helpful if the ammunition were only available for purchase in person at facilities ran by the federal government. This could be paid for by the other portion of the price increase and would create many jobs.
The tax revenue could be used for mental health screenings and treatments.