From Home Gunsmith Forum user rhmc24:

Using chambers cut off 12 ga. scrap barrels and a new $10 bbl for an Italian auto shotgun, the only other gun part is a scrapped hammer from a 1857 Remington perc revolver. Loads like a SAA Colt but underlever rotates and cocks it. Blow-by is negligible, hardly noticeable with normal shirt sleeve.

Click through to the forum to see internal shots of the action and read more about how it’s put together. [via Hack a Day]