WOW.....I must be an exception, I had a terrible experience w/them, but maybe I'll give another go since all these people have had good experience with them.
When did Federal law to buy handgun ammo (you must be 21) change ? If it's interchangeable ammo and the dealer is convinced it's for a rifle , 18 is the age. That might be questioned if it's 9mm. Stores will make you show ID if buying ion person, if it's shipped and required for the reciever to be 21 and the UPS or whoever driver does not know you , you will likely have to show ID. An old fart ;like me, not so much.
From the ATF website
Q: Does a customer have to be a certain age to buy firearms or ammunition from a licensee?Yes. Under the GCA, long guns and long gun ammunition may be sold only to persons 18 years of age or older. Sales of handguns and ammunition for handguns are limited to persons 21 years of age and older. Although some State and local ordinances have lower age requirements, dealers are bound by the minimum age requirements established by the GCA. If State law or local ordinances establish a higher minimum age, the dealer must observe the higher age requirement.
[18 U.S.C. 922(b)(1), 27 CFR 478.99(b)]
Q: May a licensee sell interchangeable ammunition such as .22 cal. rimfire to a person less than 21 years old?Yes, provided the buyer is 18 years of age or older, and the dealer is satisfied that it is for use in a rifle. If the ammunition is intended for use in a handgun, the 21-year-old minimum age requirement is applicable.
[18 U.S.C. 922(b)(1), 27 CFR 478.99(b)]