That is a great clip. About a year ago I saw a video of a guy doing nearly the same thing with a rifle on an indoor range. It blew right out of his hands and the rifle went on the floor. I hope someone can repost the link if they remember it.
I about did that about a year ago with a new Ruger Super Blackhawk. I shoot one handed and it was real cold out and my skin was really dry. I usually shoot S&W's with Hogue grips. They never slip. For best accuracy I have adopted a very light grip. It also saves my wrist from taking a beating with heavy loads in my 5" 629. Well my buddy hands me his slick wooden gripped Blackhawk and I didn't think a thing about the slick grip or that it was a 44 mag. First shot that thing flew right out of my hand and the muzzle hit me in the neck right besides my adams apple. I caught it before it hit the ground. It was a real surprise for both of us as we have been playing with guns with each other since 5th grade. We are both over 40 now. After I convinced him I could really handle it I can still shoot it better than he can but you can bet I damp my fingers before I shoot. He still gives me heck about it whenever he thinks he can embarrass me with it.