Varies by country. In the US, it's 18 for Title I long barreled firearms (rifles and shotguns), and 21 for handguns and Title II NFA items (machine guns, short barreled rifles, suppressors, etc).
i had a look and they are illegal
any age
there legal
18
8
no its a criminal offence
Unless your state has restrictions, 18.
If you are not a felon, then the legal age is 21.
You need to talk to a lawyer for a correct, legal and current answer.
Owning a gun is not illegal if you follow the laws.
Think about the legal age to buy a gun. It's probably around that age.
Hand gun - 21; long gun - 18