Ammunition is sold to extremists and mentally ill people because it is easy to buy.
Ban US companies from making, selling, and even importing ammunition of all types (from all countries, including our allies). Also ban all other actions promoting or enabling any actions in the US. (Permit US mfr for only military with rigid accountability.)
Without a total ban, force buyers (hunters, too) to: wait for a mandatory background check; show sellers a valid government issued photo ID (e.g. driver's license) that sellers must photocopy; meet a high minimum age (e.g. 25yrs old); pay high taxes, as high as cigarettes.
The 2nd Amendment was created to protect citizens when no state militias existed. Today we have national guards and police. Hunting is not the issue.