A so-called “high capacity” magazine is an ammunition feeding device which accepts, or can be easily modified to accept, more than ten rounds of ammunition or more than five shotgun shells. It is also that which is defined as such by 18 USC 921(a)(31), as it appeared when the federal so-called “assault weapon” ban was passed on September 13, 1994. Although the federal ban has since expired, the Massachusetts “high capacity” magazine ban lives on. Tubular .22 caliber ammunition feeding devices are not considered high capacity magazines.
The mere possession of a high capacity magazine without a Class A License to Carry Firearms is a crime. Also, for the possession of a high capacity feeding device by a non-law enforcement official to be lawful, it must have been lawfully owned or manufactured prior to September 13, 1994. In Massachusetts, it is unlawful for a private citizen to own a high capacity magazine which was not lawfully possessed prior to that date.
G.L. c. 140 § 131M makes it a felony to “sell, offer for sale, transfer or possess” a high capacity ammunition feeding device or magazine that was not lawfully possessed on September 13, 1994. There is an exemption for active duty and retired law enforcement officers. These magazines may be referred to as “post ban” magazines, with those being lawfully possessed prior to September 13, 1994 being referred to as pre-ban magazines.