Much in the same way sin taxes are used to pay for the social ills of tobacco and alcohol, raising taxes on firearms and ammunition could raise the prices to discourage casual purchases and result in many benefits including using the funds to pay for much needed programs chiefly:
Nationwide gun buyback programs that could result in millions of guns off of the streets in the next 10 years.
Funding the much needed additonal background checks on internet and non-gunshop purchases.
Creating a national database of those who already own assault weapons that can be scrubbed by the FBI so that the legality of ownership can be periodically checked.
Create a tracking system for large puchases of ammunition that is similar to the tracking of large cash withdrawals from financial institutions.