The force behind the missile and the size and angle of the missile’s arc are the two major factors which affect the accuracy and firing distance of a catapult the most. You have to take certain measures to adjust these two components of the catapult and desired results can be achieved.
The force exerted behind the firing object directly depends upon the weight attached to the opposite of catapult. It actually creates tension and when the catapult is released, this balancing weight swings the arm and throws the object to its target. The tension in the catapult’s arm can be increased by cocking the catapult to a different level. More backwards you pull the level, greater will be the force of tension and firing distance will improve significantly.
The elastic used in the sling also affects the throwing power of catapult. Using shorter and more powerful elastic bands add more tension to the firing object during drawback.
Using a heavier counterweight on the opposite side of the swing arm will increase the force of the catapult to a great extend. The force of gravity will play its part when a heavier counterweight is placed and this will stock the throwing object with more kinetic energy.
Extending the length of the swing arm will make the arc larger and this will launch the projectile further. It should also be kept in mind that increasing the length of swing arm will also require to place a heavier counterweight otherwise the modification might fail to yield the desired results.
The stop bar of the catapult can also be raised and this will increase the swing arm’s range of motion and fire the projectile to a longer range.