Hi -
The length of the ribbon can be controlled by the lifetime of the particle system in the required module. Remember that these should be quick effects, so a lifetime of 1 is really long for a gunshot.
Assuming you setup your material and particle like I have in the tutorial then all you would need to do it increase the Initial Color settings to a higher value and that will translate into a more emissive (“brighter”) trail.
In Tom Looman’s youtube linked above, I assume that he is spawning multiple particles in rapid succession with a very high value Emissive setting as mentioned above and a very short ribbon effect.
Thank You
Eric Ketchum