Depends on the state.
The types of ammunition that can be bouoght at CCI Ammunition has no limits because they list thousands of sellers that provide every type of ammunition to the consumer for their convenience.
Breathing Apparatus Sign
Any Winchester 308 ammunition will work for you.
Where can you buy .38 rimfire ammunition from
go to the store and look in the top right corner, you can buy ammunition from there.
E5 and Above
You can probably find this at whatever store you buy ammunition at regularly. There might also be a food online options as well.
Not legally.
18
E5 and Above
Maybe. At least one major on-line seller of ammunition will not ship to Maryland.
Depends on what you are buying, where you are buying it and your age.