Particle: Stretched Billboard pulls my particles inwards ?!?

I am creating a particle system for muzzle flashes. So far, so good. After some experimenting, I discovered that the Stretched Billboard render type looks best because of the trails the particles leave. However, if I select this mode, large particles spawn from far around the emitting mesh and travel inwards to it before the actual particle burst as I wanted it occurs, resulting in a sort of “sucked in - blown out” effect. What am I doing wrong?

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Try changing your Length Scale (or Speed Scale) to a negative number (they’re in the Renderer module).