Your retired credentials, and LEOSA card are all you need. Politically speaking, the boots-on-the-ground LEO's up here are not interested in jamming you up over what magazine you have. Atty General Maura Healy re-affirmed that LEO's are exempt from provisions of the State AWB and high-capacity mag ban. I'm a LEO and state certified police instructor/LEOSA instructor. PM me if you'd like to