This gets sticky. Legally speaking, you're only supposed to buy handguns
from your primary residency.
IMO, wherever your drivers license is issued out of, is your "real"
residency. If you stay in ME for more than 90 days at a time, I believe,
you can claim, that at least for a portion of the year, that is your
"residence. " But it will be awfully hard to get a local dealer to sell you
something without a DL from that state.
It's a lot stickier than that, but mechanically speaking, thats the way
I see it- unless you have a DL from the state you're buying the guns
in, it's going to be difficult. (Well, with the exception of rifles and
shotguns, but there really isnt the same level of restrictions on those, obviously).
Also, don't forget that you cannot bring "post 94" aw's back into
MA, regardless. (eg, those nice new ARs you see with the birdcages
and collapsible stocks on them, etc). But there's nothing stopping
you from keeping those kinds of guns in ME.
Do some searches- there are some pretty huge old threads on this board
about this particular issue.
-Mike