3rd trivia point on the GS page: "Gambol Shroud's pistol form resembles a Glock pistol. In fact, the textures for the weapon note it as a Glock 19." If you are talking about Gambol Shroud then it's some sort of pistol. Definitely not a shotgun though.
As for what sound it uses... I can't really help you with that. But I am curious now.
(Note: I originally posted this, i just didn't sign in at the time)
I am referring to Gambol Shroud, excuse my vagary, but if test and listened to several Glock pistols in search for this mysterious sound, but i've turned up fruitless. That said, It just sounds a bit to ....deep, bassy, loud I want say. Too powerful, if you get what I mean. Nothing like a pistol, or at least, none i've ever heard