I think the length of time it takes after the interview really depends on how big a backlog they have at any given time. I got my first non-resident permit last March. I had my interview in December 2017 and it took 79 days from the interview until I received my permit. My guess would be yours will take between 70 and 85 days but you never know if you happened to apply during a time when there were not many applicants it could be quicker. My renewal this year was processed in under 2 months, I did wait a little too long before I sent in my renewal so I was pleased with the relatively quick turn around time. While Mass has some of the toughest gun laws and the process is more complicated than a lot of states, everyone I have interacted with in the process has been very professional, helpful and never made me feel like they were looking for a reason to not give me a permit.