Only the Gunsmith artificer is proficient with the Thunder Cannon, correct?

@DorianXander @JeremyECrawfordOnly the Gunsmith artificer is proficient with the Thunder Cannon, correct? Can other classes gain prof in it? i wouldn't allow it – i'd use DMG rules for firearms if everyone wants to get all shooty #WOTCstaff

— (((Mike Mearls))) (@mikemearls) January 10, 2017