The way it is in MASS depends on your LTC.
A LTC A allows carrying while under your direct control (on you).
A LTC B does not allow carrying a loaded gun. The gun has to be in a lock box, trunk or other secure container.
If you have a loaded gun in say a seat holster / dash holster / or in the cup holder, if you get out of the vehicle you are no longer "In Direct Control" of the gun and must store it in a container.
Here's the Chapter/Section..... Chapter 140 Section 131C
General Laws: CHAPTER 140, Section 131C
Section 131C. (a) No person carrying a loaded firearm under a Class A license issued under section 131 or 131F shall carry the same in a vehicle unless such firearm while carried therein is under the direct control of such person. Whoever violates the provisions of this subsection shall be punished by a fine of $500.
(b) No person carrying a firearm under a Class B license issued under section 131 or 131F shall possess the same in a vehicle unless such weapon is unloaded and contained within the locked trunk of such vehicle or in a locked case or other secure container. Whoever violates the provisions of this subsection shall be punished by a fine of $500.
The way the law reads the gun has to be unloaded and stored, it doesn't say anything as to having the ammo in the same container or not.
The way I do it, to be safe, incase a LEO wants to look in my vehicle or if someone breaks into my vehicle, I store my gun in one lock box and ammo in another lock box.
I carry every day, the only times I have to leave my gun in my vehicle is if I go into a Post office, Police Station or somewere else that doesn't allow carrying. In all my days of carrying I can count on my hands how many times I have had to leave the gun in my vehicle.
Folks that have to go to court everyday or somewere that doesn't allow carrying of course are different, if the place you are going dosn't have storage area's you have to lock it in your vehicle.
I worked at a College, so of course I couldn't even bring a gun with me to work unless I parked on the street (which was not something I could do). Those days sucked as I had to go about my daily travel before and after work without protection.
The LTC laws are Chapter 140 Section 131
General Laws: CHAPTER 140, Section 131
I hope this helps you out some, I am in no way a lawyer, so I am not saying this is the law, but it is how I look at the law to protect myself. Each LEO looks at the laws differently and each Cheif has his/her own thoughts of the laws and each DA has his/her thoughts about the laws.
Welcome to the Messed Up CommYwelth of MASS Gun Ownership Laws......................
If you start to carry daily it might be a good idea to contact a firearms lawyer and go over a few things with him/her, and put him/her on retainer.
David