Force weapons are potent psychic weapons that can only be used by a trained psyker such as a Librarian.
They are treated as a power weapon but can unleash a psychic attack that kills an opponent outright.
Roll to hit and wound as normal, taking any Invulnerable Saves if available. Then, as long as one wound has been inflicted, make a single Psychic test for the psyker against one opponent wounded by the weapon. The normal rules for using psychic powers apply, and you may not use another psychic power in the same turn. If the test is passed then the opponent is slain outright, no matter how many Wounds it has (but count the actual number). Force weapons have no special effect against targets that don't have Wounds such as vehicles.