Continuing the theme of the
.308Win Cross Section, here's a cross section of a 12 gauge 70mm (2 3/4") shotgun shell, scaled to 300% of the actual size.
Assembly should be straight forward, all pieces have their place, and only fit in one way (use the pictures as reference)! Gluing all parts is recommended.
Check out my other designs here: https://www.thingiverse.com/Superbeasti/designs