The way I read this, is that if you have enough ammo (spelled out in 1.12.8.50) to require a permit, you do not need a permit if you keep it in a locked container.
1) check 1.12.8.50 to see if you need a fire code permit by exceeding the ammo limits
2) if so, under 1.12.8, which category do you fall under
3) ammo falls under 1.12.8.39 ( Blasting, Explosives, Fireworks, and Model Rocketry.)
4) under 1.12.8.39.1.1.4 (2) a permit is NOT REQUIRED if "stored in original containers and stored in a locked cabinet, closet or box when not in use"
thus, you only need the permit if you exceed those limits AND do not keep it in original containers AND it's locked up in a storage container.
Otherwise, there is no storage requirement for ammo under 527 CMR 1 (Fire codes).
This is contrary to what GOAL says on their website where they don't distinguish the limits that require a permit.
GOAL - Ammunition Info
Although I believe the NRA/NSSF/etc recommend locked storage separate from firearms for safety.
I don't believe there is any ammo storage requirement under the firearms laws. I'm not 100% sure on that one.
Would love a lawyer to confirm or deny my interpretation...
@nstassel ??