Here's a question: What would happen if you carried your scary rifle around (where legal) in a properly locked case that happens to be clear/transparent so people can see it? I know I know - SWAT response, face down on the ground, loss of LTC, etc etc... but are you breaking any MA law? Perhaps they'd try to hit you with brandishing or some b.s.
Do you mean by "carry," on you person?
If it's on you person, then the law requires that it cased, and unloaded, unless lawfully engaged in hunting. Locked is not part of the laws.
There is no "brandishing" statute.
Of course a few years back, a SWAT response was called, for a guy with an umbrella, at Burlington Mall:
Man with umbrella causes rifle scare in Mass. mall
So....as I've said before...if you have to ask, you know the answer
Your title says, "Transport"
If you mean in your vehicle, the rifle, if not large capacity, merely needs to be unloaded. There is no MGL requirement for it to be cased, or locked.
That said, see the linked article.
BTW, I'm the one that coined the term, "Massprudence"