Tax gun powder sales in the same way tobacco is taxed.

Gunshot wounds cost healthcare billions annually. If we can tax tobacco to offset the cost to healthcare, we can also tax gunpowder. Further, if gunpowder is more expensive, folks are less likely to indulge five year old children with such a lethal toy which is so expensive to maintain. Unemployed teenagers are less likely to afford ammunition with which to shoot up their schools. There are many other situations which expensive gunpowder could possibly have an effect. Such a tax would increase federal revenue, perhaps create federal jobs in collecting & distribution of said tax. I'm sure there are many benefits to such a tax that I cannot think of, nor can I think of any legitimate reason gun enthusiasts & lobbyists could possibly have to excuse opposing such a tax.