MA has a 4 gun per year limit on private sales (defacto gun registry in this state). I'm ok with that because someone doing so is probably trying to be in the business of a dealer.

I've only ever bought one gun here from a private sale, a glock 26 because glocks of any kind are unobtanium usually (we also have an approved sale roster and Glock isn't on it.)

I bought mine from a NH resident who had moved here but was moving back to NH and knew he could turn my $680 for the g3 and 8 magazines into a new G5 and 6 magazines just by moving back to NH.

Also negotiated through reddit back when that was a thing.