For those that are interested, here's the language for the DC 10 round magazine limit.
No person in the District shall possess, sell, or transfer any large capacity ammunition feeding device regardless of whether the device is attached to a firearm. For the purposes of this subsection, the term "large capacity ammunition feeding device" means a magazine, belt, drum, feed strip, or similar device that has a capacity of, or that can be readily restored or converted to accept, more than 10 rounds of ammunition. The term "large capacity ammunition feeding device" shall not include an attached tubular device designed to accept, and capable of operating only with, .22 caliber rimfire ammunition.
No person in the District shall possess, sell, or transfer any large capacity ammunition feeding device regardless of whether the device is attached to a firearm. For the purposes of this subsection, the term "large capacity ammunition feeding device" means a magazine, belt, drum, feed strip, or similar device that has a capacity of, or that can be readily restored or converted to accept, more than 10 rounds of ammunition. The term "large capacity ammunition feeding device" shall not include an attached tubular device designed to accept, and capable of operating only with, .22 caliber rimfire ammunition.