Laws for selling privately

[Ghost_2.0]

Buying handgun ammo is a different story. You have to be 21 most cases at places I've seen

 

[Nwcid]

18 is legal for private sales. 18 is not legal for FFL sales. All firearms sold across state lines have to go through an FFL on the buyr's side of the state line.

That is not true. You can buy a long gun in ANY state where that gun is legal in both states. Of course it has to be bought at an FFL since you can not do FTF across state lines.

ATF Online - Firearms - Frequently Asked Questions - Unlicensed Persons Sections 1 and 2 are what you are looking for.

 

[Nwcid]

Buying handgun ammo is a different story. You have to be 21 most cases at places I've seen

This only applies to licensed sellers, 27 CFR 478.99 - Certain prohibited sales or deliveries. | Title 27 - Alcohol, Tobacco Products and Firearms | Code of Federal Regulations | LII / Legal Information Institute

There is really no such thing as handgun ammo anymore. Other then a few odd calibers most have been used in long guns over the past few decades. So LEGALLY if you are between 18 and 21 they can sell you say 9mm ammo as long as they believe you are not going to use it in a handgun.