IIRC, yes. You only need to add your weapon in the Tacticstypes.ini file. Small fighter craft are an exception I think, needing (at least) two entries in this file. For craft itself, and the weapon it fires.
But also, IIRC, I think you need to restart a whole new campaign to see the changes ingame, as the tacticstypes.ini file info is 'hardwired' into the save of a campaign.