The weapons were powerful enough to injure or kill a Q. After entering the Q Continuum, Janeway was able to help Q move and avoid some of the fire. Q stated concern over what the result would be of a Human being hit by the weapons.
Once the USS Voyager and its crew entered the Continuum, Q and the female Q were able to equip them with Q weapons and they were able to use them to battle the opposing Q representing the status quo. (VOY: "The Q and the Grey")