Shorty, if you're in California...just wait till you get caught with that...ya fucking terrarest!!
Apparently, it's legal to own them...but illegal to buy or sell them...??
http://wiki.calgunsfoundation.org/index.php/Large-capacity_magazine_restrictions
Large-capacity magazines
Large-capacity is legally defined as 'greater than 10 rounds'.
It is illegal to sell, manufacture or import large-capacity magazines.
It is legal to own, possess and use large-capacity magazines.
It is legal to purchase, own and possess 'parts kits', so long as such kits are never assembled into magazines inside California.