From the Super Mario Wiki
Retrieved from "https://www.mariowiki.com/index.php?title=Klap-Blaster&oldid=2497420"
Instead of regular ammunition, Klap-Blasters shoot a barrage of Klaptraps which can chew through almost anything. However, Klap-Blasters are occasionally seen to shoot explosive projectiles.
Oddly, it is never explained how a Klap-Blaster can hold so many Klaptraps when the weapon's ammunition holder is actually extremely small.