In this tutorial I cover how you can create your own custom weapons for your games for FPS or TPS games. The same principles could be applied to any other weapon you want to create, for instance on a tower defense map you could do the same but trigger the weapon with an ability.
But this doesn't use any actors, it's pure triggers. There is an action that lets you pick the position of an attachment as a point, but it doesn't come with any presets so I can't specify any attachment points. I can enter them as text but I don't know what strings to use, nothing I've tried works.