A while back, I bought myself a 3D printer; with this printer, I created a penny shooter; this penny shooter is devised of several parts, the chamber, handle, rail, rubber band, and the trigger system. When the chamber is pulled back, it catches on the trigger mechanism. The force of the rubber band wants to pull the chamber forwards but is stopped by the trigger mechanism. The energy is instead diverted to the trigger. When the trigger is released, the chamber rapidly moves forward on the rail until it hits the end, the chamber stops, but the penny inside the chamber will continue to move.

This is more of a thought experiment, but this gun is not very strong, so the chances of it breaking anything are slim. What would I need to alter in order for this gun to be strong enough to break through a typical window?

My hypothesis could be that if I make the rail longer, it will gain more speed, causing the penny to fly faster.

If I were to make the rail longer, I could put more tension on the rubber band, which in return would cause the chamber to reach a higher rate of speed, but rubber bands only stretch so far before they inevitably break. I do not believe I could stretch this rubber band enough to cause a window to break. I believe I would have to upgrade the rubber band to a brand that is more on par with a slingshot. Right now, the full extension of the shooter is roughly 3 inches. If I used a better band and extended the rail to about 12 inches, I believe I could shoot a penny fast enough to break a window. The body of the shooter would have to be re-enforced because I believe the pressure from a stronger band would cause the body to fail