YouTube has removed the video
quotingA Belt-Fed Shotgun Is a Terrifying, Beautiful Thing
note1s0u…z66f
The video shows a stubby-barreled gun firing firing continuously from a belt of 12 gauge ammunition. The upper receiver of the gun appears home-made, while the lower appears to be a standard AR-15 rifle lower receiver.
https://www.popularmechanics.com/military/weapons/a20154/yes-a-belt-fed-shotgun-is-a-thing/
