you don't need an FFL to produce and sell bullets.
You do need the required business licenses and permits to sell bullets (just the projectiles) Also local zoning and environmental laws apply.
Same as selling anything else.
"Manufacturing" loaded ammunition requires all that PLUS the Federal licenses, which are not exactly the same FFL as the one needed to run a gunshop.
If you are making ammunition, then you are a manufacturer and other requirements apply, including various taxes that are only applied at the manufacturer level.
There is a set of licenses to make the stuff, and another set to sell it as a business.
And, that's not even counting the various insurance needs that must be met...
The guy selling a few reloads at a gun show or flea market usually doesn't get busted, but COULD BE.
The guy doing it as a commercial business without ALL the needed licenses, WILL BE busted, particularly if he makes any money at it, and fails to give the govt their share.