How old do you have to be to own an assault rifle in the state of California?

Answer 1

For a true assault rifle, with select fire options (e.g., burst, full auto), you had to be 21 by 1989 - the year California's Draconian gun laws began going into effect. Meaning you'd have to be 45 to be old enough to have been a California resident before NFA permits ceased.

For a semi automatic rifle with "evil" cosmetic features, you had to be 18 by 1989, meaning one would have to be around 42 to be old enough to have been a California resident who owned such a rifle at the time.

By the way, California also banned the importation of either of the above mentioned types into their state after 1989, and required registration of semi-automatic firearms designated as so-called "civilian assault weapons" by 2000.

It is possible for a California resident to own an AR, AK, etc. platform rifle, however. There are two methods of doing this. The first is the bullet button. It requires the installation of a magazine release which must be actuated by the tip of a bullet or tool of some other sort. Legally, this makes it a fixed magazine rifle, and you can have all the banned cosmetic features with it.

The other method is a featureless rifle - no pronounced pistol grip, no collapsible buttstocks, no flash suppressor, no vertical forward grip (and, according to a California Department of so-called Justice ruling, Magpul's Angled Forward Grip is considered a forward grip, and is thus banned in California), no thumbhole stocks... the advantage to this, however, is that you can have a semi auto detachable magazine rifle, and it is possible to acquire magazines over ten rounds in California, as their magazine laws have holes you could quite literally drive an armored truck through.

Additionally, it must be built on an off-list lower, meaning it can't be made by a manufacturer banned on the CA DOJ's list of banned receivers.

As with any Title I long gun, you must be 18 to own one of these, in accordance with federal law.

Answer 2

A transferrable, select fire rifle can be bought by anyone who is 18, has the cash and complies with all federal, state and local laws.