I think its depends on who the owner is. If both Actors are spawned on the server (ie The gun and the projectile), it will work as expected since the client will simply be replicating the position from the server. If both are spawned on client instead, same logic applies.
But if one of them is spawned at server and the other on client, then I am not quite sure. I haven’t tried that yet and unfortunately I cannot test it anytime soon. But I would say it might not work.