This is a remix of a nicely working cannon by https://www.thingiverse.com/makkuro
The device is all print in place, with hinges, a spring, and a moving plunger.

I've added some geometric fancy, smoothing the end of the cannon, and rounding all sharp corners. The slope of the side walls is also a bit more printer friendly.

All the stuff you see is under copyright. Proper credits go to mr_HU5KY