Summary

A remix from https://www.thingiverse.com/thing:603697
I Use 1 M3 25mm and 1 M3 20mm ( or 2 M3 10mm)
Add a version with view finder to redirect and aim better

Print Rubber_band_gun-Barrel_hole.stl and Rubber_band_gun-ViewFinder.stl for Viewfinder version

Print Rubber_band_gun-Barrel.stl for regular version

Assembly guide: https://youtu.be/IndIVcwJN20

Print Settings

Printer Brand:

Anycubic

                                            <p class="detail-setting printer"><strong>Printer: </strong>                     <div><p>Kossel Linear Plus</p></div></p>                                                                                <p class="detail-setting rafts"><strong>Rafts: </strong>                     <div><p>Doesn't Matter</p></div></p>                                                                                <p class="detail-setting supports"><strong>Supports: </strong>                     <div><p>Yes</p></div></p>                                                                                <p class="detail-setting resolution"><strong>Resolution: </strong>                     <div><p>0.3</p></div></p>                                                                                <p class="detail-setting infill"><strong>Infill: </strong>                     <div><p>20</p></div></p>                                                    <strong>Filament:</strong> Kingroon PETG, PLA

Post-Printing

                <p class="detail-image"><img src="https://cdn.thingiverse.com/assets/36/b9/28/3e/da/a898bbb9-5054-4bc9-bc15-3184f0be7f0b.jpg"></p>                <p class="detail-image"><img src="https://cdn.thingiverse.com/assets/6c/32/e9/68/a7/6f37f3c8-2ae4-494c-956d-b5aeac38439a.gif"></p>

Rubber band gun