PART I. ADMINISTRATION OF THE GOVERNMENT
TITLE XX. PUBLIC SAFETY AND GOOD ORDER
CHAPTER 140. LICENSES
SALE OF FIREARMS
Chapter 140: Section 121. Firearms sales; definitions; antique firearms; application of law; exceptions
Section 121. As used in sections 122 to 131P, inclusive, the following words shall, unless the context clearly requires otherwise, have the following meanings:-
“Assault weapon”, shall have the same meaning as a semiautomatic assault weapon as defined in the federal Public Safety and Recreational Firearms Use Protection Act, 18 U.S.C. section 921(a)(30) as appearing in such section on September 13, 1994, and shall include, but not be limited to, any of the weapons, or copies or duplicates of the weapons, of any caliber, known as: (i) Avtomat Kalashnikov (AK) (all models); (ii) Action Arms Israeli Military Industries UZI and Galil; (iii) Beretta Ar70 (SC-70); (iv) Colt AR-15; (v) Fabrique National FN/FAL, FN/LAR and FNC; (vi) SWD M-10, M-11, M-11/9 and M-12; (vi) Steyr AUG; (vii) INTRATEC TEC-9, TEC-DC9 and TEC-22; and (viii) revolving cylinder shotguns, such as, or similar to, the Street Sweeper and Striker 12; provided, however, that the term assault weapon shall not include: (i) any of the weapons, or replicas or duplicates of such weapons, specified in appendix A to 18 U.S.C. section 922 as appearing in such appendix on September 13, 1994, as such weapons were manufactured on October 1, 1993; (ii) any weapon that is operated by manual bolt, pump, lever or slide action; (iii) any weapon that has been rendered permanently inoperable or otherwise rendered permanently unable to be designated a semiautomatic assault weapon; (iv) any weapon that was manufactured prior to the year 1899; (v) any weapon that is an antique or relic, theatrical prop or other weapon that is not capable of firing a projectile and which is not intended for use as a functional weapon and cannot be readily modified through a combination of available parts into an operable assault weapon; (vi) any semiautomatic rifle that cannot accept a detachable magazine that holds more than five rounds of ammunition; or (vii) any semiautomatic shotgun that cannot hold more than five rounds of ammunition in a fixed or detachable magazine.
Source - http://www.mass.gov/legis/laws/mgl/140-121.htm