This;There is already a federal 11% tax on ammo and firearms accessories that goes directly to national natural resources preservation.
What makes you think an additional 9% at the state level would be ruled Unconstitutional?
If it has been challenged and upheld that may be something.Taxes specifically targeted to burden inalienable rights such as poll taxes or newspaper printing ink have been found unconstitutional in SCOTUS opinions. Therefore taxes on "The right to keep and bear arms." are likely to also be found unconstitutional.
"The Federal Aid in Wildlife Restoration Act (also known as the Pittman-Robertson Act (PR)) became law in 1937" This is an excise tax at the wholesale level that was requested by the firearms and ammunition industry specifically targeted to wildlife preservation so it has not been challenged as far as I know.
Link to NSSF PDF: