Quote Originally Posted by nickl_2000 View Post
Based on this in the player rules

What rules sources are legal for the Oracle of War
campaign?
Currently, the following sources are legal for the campaign:
• Player’s Handbook
• Xanathar’s Guide to Everything
• Tasha’s Cauldron of Everything
• Eberron: Rising from the Last War
• Volo’s Guide to Monsters
• Mordenkainen’s Tome of Foes

Other resources may be opened by campaign documentation
such as Adventure Records or special event certs.



Since the DMG isn't in the listing of legal rule sources and rules for firearms aren't mentioned anywhere in Xanathar's or Tasha's I would guess that it's a no.
I have no idea how AL works in general or that campaign specifically, but if you can't, you can't. I'd ask your GM, if possible. Both TCOE and ERLW mention them as optional rules, but I'm vaguely aware AL attempts to standardize tables across multiple GMs, so it would make sense for there to be a definitive answer outside of your GM's control.