You're asking the question nobody can answer. They are on the approved roster but the attorney general's non-existant list says you can't sell them. An ffl was recently just denied their renewal due to selling non-ma compliant guns so even those who are normally willing to sell glocks aren't right now.
The real kicker is that they use consumer protection laws to deny the sale or glocks. Yet they allow police officers to carry said unsafe firearms on duty.
Where are the lawsuits???
I also live in mass & am a Glock fan.....any Glock purchased from an Ffl dealer has to be made before 1996 which pretty much means all Glock sold here are gen 1 or 2 & they are usually overpriced.....I have a gen 2 Glock 21 & 17....both in amazing condition but it took a while to find them online out of state & had them shipped to a local Ffl dealer....check out four seasons gun shop.....great to deal with & usually a good selection of used glocks
Maybe MA has a law like CA does: the Magazine Disconnect Safety Device (MDSD) law. The device is configured so that if you disconnect the magazine from the pistol, you can't fire the round left in the chamber. All 4th Gen Glocks are off roster in CA for that reason.