At the beginning of his review videos Jeff Quinn has a short intro where he is shooting some guns. (Dagnabbit! You kids stay off my lawn!
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Anyway, the second gun he shoots is a revolver that he shoots single action.
The recoil looks pretty sever. More so than even a .44.
Any idea as to what make it is, and what caliber? Could it be a .500?
We’re talking about the 2nd one at the start? The lack of grooves (what is the word?) on the cylinder makes me think it’s not S&W models 500 or 460. In .500 caliber it turns up rather custom jobs, no big-name manufacturers. The shape is hard to tell, does it look like single action? But shape doesn’t always suggest function. Single action would generally suggest a less modern caliber.
I thought grooves were only a way to reduce weight and makes it easier to rotate the cylinder by hand. Overall I know of no real important reason for them.
He’s firing it in single action mode. Whether the gun itself is single action I know not.
But he is a well experienced shooter and that gun seriously barks. Watch how his right hand jerks after firing. I’d be surprised if it’s only a .44. Unless he was using some kind of hot load.
According to his video archive, it’s the “Lipsey’s Exclusive Ruger Bisley Super Blackhawk 44 Magnum with 3.75 Inch Barrel.”
It appears you are right. Thanks. 
Even for a .44 that thing barks. Wonder what he was shooting out of it.