Chuck can shoot fireworks at enemies at a relatively fast rate, clearing hordes of zombies with a short burst. The fireworks need to travel a small distance to be lethal, so Chuck should not fire them point blank or they will just bounce off an enemy before going off. Getting stuck in an explosion causes Chuck to drop the weapon.
The Rocket Launcher has a small advantage over most other heavy weapons in that it has no motor that requires starting before it can be used, Chuck can simply pick it up and start firing.
"Not quite what you're thinking. A series of pipes fires off the fireworks inside. They aren't super accurate, but they do explode limbs like a charm."[1]