This is a boxing tool for 20 gauge shells based on the 12ga box loader by ductape. His design appears to tilt back and also have a slant. Mine won't have the slant but does tilt back. I have tried it with a vintage Federal Hi-Power box and a newer Federal Field & Target box. Can be a little tight but it worked fine and inserted just about the entire internal volume of the box.

Creality

Ender 3 Pro

No

No

0.2

10%

Print on it's back and requires no supports and no cleanup. I did 3 walls. You could increase walls and/or infill and maybe make it stronger or more durable.