When you say "weapons fire", do you mean particle effects? Or just the tga and dds files associated with them? Do you have particle forge?
Anyway, particle pipeline effect "particleAdditive" displays black as transparent, and grey as semi-transparent. Whereas "ParticleNotAdditive" displays all particle color channels except null ones. ParticleAdditive, when multiple effects are stacked on top of each other, they pile to create a brighter whiter color or any color that the emitter is changed to. Thus creating a "glowy" effect. ParticleNotAdditive does not stack emitter-wise and cancels any emitters under it. It also holds priority over ParticleAdditive and will always cover that kind of emitter.
Sorry if this was worded oddly, i was trying to think of ways to describe this.
This also may have been useless information to you...