There are no bullets in FPSC, the engine just draws a line (raycast) from you to the nearest object and causes damage and bullethole.
Rocketlaunchers and grenades use "flak" which makes a moving object come out of the gun, but the effect of them is hardcoded; they always explode. They also have a nasty habit of chain reacting, so if lots of them were close together, they'd explode in a big line back to you.
So technically, no, that effect will not work. There are some variations however:
Butterfingers attempted a flamethrower. It looks awesome, but he never told us how to do it. I have the feeling he never will, either:
http://uk.youtube.com/watch?v=g-SFHKYTRh0
You can make the flame part of the model. It's a crude method and means the flame is affected by the level light, but it works

Here's an example that I made:
http://uk.youtube.com/watch?v=HNzUNAcZKhY
Best,
Paul