Board Thread:Off Topic/@comment-27144409-20181126150808/@comment-25396609-20190115062948

This is the M6 Aircrew Survival Weapon, a fully collapsable over-under rifle chambered for .22 hornet and .410 gauge shot shells.

When folded it is approximately 15 inches long and substantially narrower.

You could easily fit a single-barrel semi automatic or fully automatic rifle inside of 12X19 inch book with room to spare for a magazine and stored sight of some description. The hardest part is arguably what to do with the book parts, but they can be made of collapsable panels as a shell.