Thanks Bob - explains the reduced recoil difference - was thinking .577 NE. I expect it was still a hell of a shock to the shooter. My right shoulder aches just watching it.

I re-watched the video - noting where the fellow was holding the forend. I see the forend appears, in the video, to be quite 'proud' (large) and appears the gun was not held by the barrels as it would be at the end of a sort splinter forend. I believe that would improve pointing ability to start with and muzzle control secondly.