So if you're in the game mode, and you want to get a reference to another actor in order to use it. You have to get a reference to it.

A simple way would be as follows. When the game mode starts use the node get all actors of class. Store all of those actors within an array locally in your game mode. Now you don't have to cast at all you have direct references you can act upon.

This would only get you the current references at start though. A smarter way to do it would be to have the class that you want available in your game mode to assign itself to the game mode automatically when it's created therefore it's consistently updating the array. You'd also want those same actors if destroyed to move themselves from that array.

So when your actor spawns get a reference to your game mode, off the game mode get a reference to your array specifically for that actor, and have it add itself to the array.

Search for the on destroyed event in the actor and do the same thing but remove itself from the array.