You do realise that the "lit part" is the only part making that light, right? It's not a glowing tube with a burning end, it's an illusion created by your eye and brain.

Now this is where the camera and eye start to differ, and where compression, framerate and lens quality fall short.

The tracers in Cliffs of Dover are accurate. This is coming from the people who made them, and the people who have actually seen and fired real tracers in real life!