Still a work in progress however it is a fully functioning semi auto elastic band gun. You can use a clicky pen spring for the trigger however it is not necessary as when loaded the elastic bands should offer some trigger weight. This may double fire if the tension from the elastic bands is too great so don't put anything too beefy on it. I have included a fusion 360 file so you are welcome to modify it as you like. The outside is based on a glock 19 so it's comfortable to hold and looks pretty awesome. The "sight" which you put the elastic bands on can slide forwards and backwards to offer adjustable tension based on the size of your elastic bands. It's fairly big however I managed to fit it quite happily on my ender 3 by printing it diagonally. Any questions, please feel free to ask.
20% for body, 50% for the smaller parts