I have spent a few years iterating this project. Finally it is reliable and fairly simple. This rubber band gun shoots bands from a MAGAZINE. It uses small “rainbow loom” bands, which allows the design to be compact. Unlike other repeaters or gatling guns, this mag fed gun stores its ammo unstretched. This allows multiple mags to be loaded for long periods of time without the worry of bands breaking due to fatiguing rubber. While other designs change trigger pull weight or cocking force with each shot, this one stretches just one band at a time giving a consistent racking experience. There is a hollow grip for convenient band storage and an access port in the slide for monitoring, and clearing jams. A full demo and assembly video can be found here: https://www.youtube.com/watch?v=B9_oLZ1OBtQ Skill level: Intermediate. This project requires intermediate knowledge of your slicer, E.g. support blocking and seam placement. The cleanup and assembly is straightforward. Tools: X Acto and/or utility knife Sandpaper and/or file Pliers or flush cutters for support removal Screwdrivers and or Allen keys for hardware Materials: PLA or other stiff filament Two M3 x 20mm machine screw One M3 x 14mm machine screw Two pen springs, just under 5mm OD. Two 5x5x2.5mm Magnets 60mm of 1.75mm Filament for sliding pins Super Glue 15mm wide or narrower thin double sided tape(or just glue) Rubber Bands! Dimensions: Gun. 180mm x 124mm x 32mm. Mag.122mm x 35mm x 7mm. P.S. I have no idea if the picatinny rail is functional. It it based on dimensions from online and I have never tried it. Please tell me if it works!