Hey, what I did was duplicate the Photon Cannon unit along with the Actors for: Cannon, Attack, Attack Missile and Splat... the Models for: Cannon, Attack Impact and Weapon... as well as the Weapon and Effects. So I renamed everything to reference "Antimatter Cannon" instead of Photon Cannon Copy. Changed the actual art for the Models to something I liked, made sure to have them plugged into the Attack action actor under Impact Map as well as the Missile actor.
Here's the problem. Only the missile model works in-game, the impact model doesn't show up at all. I know I probably missed some teeny tiny detail. Maybe with the Events of some actor. (I've never been great with understanding Events) I remember having this problem years ago but I guess these forums have changed quite a bit and I can't find the answer by searching.
Edit: Just tested and the impact sound isn't working either.