A Class A license authorizes carrying of handguns, including large capacity handguns, for all lawful purposes, subject to such restrictions relative to the possession, use or carrying of handguns as the licensing authority deems proper, and carrying of rifles and shotguns, including large capacity rifles and shotguns, for all lawful purposes, subject to restrictions imposed by the licensing authority. A class A license holder may carry a loaded handgun in a vehicle, if it is under his direct control. However, this does not apply to large capacity rifles or shotguns. Such firearms must be carried unloaded, in the locked trunk or in a locked case or other secure container.
A Class B license authorizes carrying of non-large capacity handguns for all lawful purposes, subject to such restrictions relative to the possession, use or carrying of such handguns as the licensing authority deems proper, and carrying of rifles and shotguns, including large capacity rifles and shotguns, for all lawful purposes, subject to restrictions imposed by the licensing authority. However, a class B license does NOT entitle the holder to carry or possess a loaded firearm in a concealed manner in a public way or place. A class B license holder may not carry a loaded firearm of any type in his vehicle; all firearms must be carried unloaded, in the locked trunk or in a locked case or other secure container.
The last sentances on both, Class A and B pretty much sum it up. IF there is no trunk, then a Locked container or other Secure container.
The two paragraphs mentioned above for Class A and Class B were taken from the MA Concealed Carry Permit Information here on USA Carry.
Other's, please chime in if I misunderstood the OP question/s.