KB

When I first saw this, it was just stills, as I was at work and not looking at the video.  But here is the video if you are one of the 4 people that haven't seen the S&W .500 blow up yet.



From the stills, my guess was a timing issue, but he shot it single action.  Less chance for a misalign there.  After seeing the video... Maybe a squib? 

Then I watch it a few more time.  Looks like some of the top strap banananas on the far side maybe?  Now my guess is over charged reload.  Shoulda prolly been my first guess.  If anyone sees the 'why' later, I'd appreciate a point out.