FTFY (pedantically).
Yes, that looks like the current edition to me.
And you quoted the relevant language, but I pedantically Linked That For Posterity.
(As quoted above), the
ammo reg. calls for "... stored in original containers and stored in a locked cabinet, closet or box when not in use".
The corresponding statute
for guns (MGL
Ch. 140 §131L) calls for "... a locked container or equipped with a tamper-resistant mechanical lock or other safety device, properly engaged so as to render such weapon inoperable by any person other than the owner or other lawfully authorized user".
So a basement with a locked door at least sounds
more Massprudent for ammo than guns.
We know that if you use a "stick a pin into the hole to bypass"-style bathroom locking doorknob
for a closet full of guns, there's Mass. case law that you're cruisin' for a bruisin'.
If it looks like Maxwell Smart's apartment door, you're rather safer.
If it
locks like
Maxwell Smart's apartment door, you're hosed.