That's one hell of a kick back. Here's the story that goes along with the video:
The gun in the video is basically a "show and tell" custom built on a Thompson Encore (fancy version of the Thompson Contender).
600 Nitro Express. That's right...an elephant gun round in a handgun. The story goes that the guy that built it is some kind of custom gun maker, and built this as an exhibition piece. He takes it to the range with him just to show it off, and the big guy that shot it (in the video) had been bugging the builder to let him shoot it. Now think about this...only until fairly recently (early-mid '80's IIRC) the 600 Nitro Express was hands down the biggest, nastiest, hardest hitting, and heaviest recoiling weapon you could buy. It was designed for one simple purpose...to knock an elephant flat on his a$$. IMO, it was really built as an exhibition piece for guys "compensating"...this cartridge is known for breaking collarbones, arms, shoulders...of the shooter! Think about this...in the gun world they use what is termed as a "recoil index" to kind of give prospective buyers an idea of what agun kicks like. A .30-06 gets a rating of a 1.0, which for many people is about the limit of what they can shoot multiple rounds thru comfortably. A .243 is rated at like a .4, a .270 was like a .8, etc.
The .600 Nitro Express is rated at a 9.4...9.4 times more punishing than a 30-06.