If you want to put a lot of lead downrange fast belt-fed automatic weapons are the way to go. Now combine that with the power of a shotgun and you have a real lead slinging machine.
Imagine loading up this bad boy with 00-buck shot and letting loose. That is a lot of firepower and would be devastating at close range.
There is not too much information on where the video came from I imagine because it’s probably illegal and I am sure the ATF would love to find it.
If you look close it appears to have an AR lower and it does jam a few times but still pretty cool.