I'm guessing he was a re-loader.  He double-charged the powder in his handloads (not too difficult to do if you're not paying attention).  

When the double-charge went off;  the gun recoiled violently enough to separate the bullets from the casings...notice the bullet in the foreground cylinder displaced fwd.   ....this spilled the powder out of each of them... (tolerances are not very tight in the cylinders) and the flame-front from the first "bang" ignited the lower two loads, causing enough overpressure to blast off the entire top of the cylinder.    

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is he okay other than having to change his drawers?

jello wrote (View Post):

is he okay other than having to change his drawers?

LOL, He said there was a loud bang when he tested his new load and the gun smacked him in the forehead, leaving a nice gash.

When the tweety birds cleared, that is what he saw.....

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