This directly from the ATF website:
Q: Is a license required to engage in the business of selling small arms ammunition?
No. A license is not required for a dealer in ammunition only, but a manufacturer or an importer of ammunition must be licensed.
[18 U.S.C. 922 (a)(1)(B)]
(I would suggest that you clear it also with the business license issuer also.)
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
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