It is illegal to sell reloads for a profit without a license. The commercial ammo reloaders such as Georgia Arms have a license.
(H4) Is a person who reloads ammunition required to be licensed as a manufacturer? [Back]
Yes, if the person engages in the business of selling or distributing reloads for the purpose of livelihood and profit. No, if the person reloads only for personal use.
[18 U.S.C. 922(a) (i) and 923(a), 27 CFR 478.41]
ATF Online - Firearms FAQs
And, from page 165 of the Federal Firearms Regulations Reference Guide:
Reloading of used shells or cartridges
is considered manufacturing for
purposes of excise tax. Sale of such
shells by the reloader is subject to the
excise tax. However, if the reloader
merely reloads shells belonging to a
customer and is paid for labor and materials,
the reloading service is not a taxable
sale, as long as the reloader
returns the identical shells provided by
the customer to that same customer. In
such instances the customer is the
manufacturer and would not be liable for
tax if the shells are manufactured for
personal use. If the customer sells reloaded
shells or uses them in a business,
e.g., shooting range, the customer
would be liable for the tax.