There is another large capacity magazine issue that only applies to LTC-B holders. For instance, an LTC-B holder could lawfully purchase a Beretta CX4 Storm carbine. But, that gun is designed to operate with handgun magazines, so the LTC-B holder could only legally purchase and possess magazines for it that hold 10 rounds or less. The same goes for LTC-B holder who want to buy an AR-15 that’s modified to take pistol magazines, or other pistol caliber carbines like the KelTec Sub-2000.
Another legal gray area involves AR or AK pistols in Mass. Because Mass. adopted the 94 AWB there’s not many (if any) legal AR or AK pistols in Massachusetts, but the issue is that some might consider the rifle magazines that fit in those pistols to be pistol magazines. If legally they are considered pistol magazines because of this, they would require an LTC-A to purchase or possess; the implication is that an LTC-B holder would be able to have an AR-15 rifle, just not mags for it that hold more than 10 rounds.
This will remain a gray area until Mass. law is modified by the legislature or interpreted by the SJC to define how it should be determined what is a rifle mag and what is a pistol mag.