Description and usage
The catapult was a device constructed of wood and ropes or leather cords and used in the siege of a city. It consisted of a base to which was attached a long wooden arm. At one end of the arm was an open bowl-like container that held the object to be projected, usually a heavy stone. The arm was forced down by mechanical means, bending the wood into a tense bow. When released, the arm snapped back into place, hurling the stone in the direction of the besieged city. The size of the stones varied widely according to the size of the catapult.
Translation

While the Greek text of 1MA 6:51 uses three words for instruments to propel objects (see Fire thrower), some translators may want to combine the three words in a more general phrase, for example, “weapons [or, machines] that threw fire and spears and rocks.” GNT provides a good model: “catapults for throwing fire and stones, and other weapons to throw spears and rocks.”