When a ranged weapon with the "Scatter" tag has two or more other tags, the projectiles will not fan out when fired. Multiple projectiles do seem to be fired, but they are stacked atop one another. The exact nature of the other tags appears irrelevant; only the total number of tags. To demonstrate, save file included contains three weapons: one with Scatter, one with Scatter,Metallic, and one with Scatter,Metallic,Piercing. First two weapons spread projectiles, third does not.