This.
The Beretta in the picture looks to be a Beretta 70, which uses magazines that have 7-10 round capacity (a single stack 7 rounder is pictured). Moreover, the trend of the Massachusetts courts has been to hold large capacity firearms as a fourth category of guns under state law (in addition to "rifles", "shotguns", and the catch-all "firearms") rather than merely a modifier of the other three categories, though to my knowlege there hasn't been any solid case law on the issue.
In my view, BPD correctly charged the large capacity firearm since, despite not being on the large capacity roster, a large capacity feeding device was found in the control of a person who also had a semi-auto weapon capable of accepting that device. See 501 CMR 7.02.
Even though the 10/22 isn't on the large capacity roster, and even if he didn't have any LCFD's, the addition of the two
'evil features' (folding stock and pistol grip), would have been sufficient to hit him with the unlawful possession charge.