Projectile weapons are mentioned as being used by the Fremen in Dune:
...in spite of its unfamiliar shape--a projectile weapon.....a chorus of spring-clicks from the basin. Projectiles whined off the rocks around him.
A "spring-click" would seem to indicate the propellant force derives from a spring. However, in another answer on this forum it is indicated (but not sourced) that the propellant is chemical, and roughly equivalent in stopping power to modern-day handguns.
Were they really that powerful? Has anyone ever guestimated the muzzle velocity and stopping power of the Fremen hand-weapons?
Were they truly lethal, or more of an annoyance?