Not mine, it belonged to a LEO that was there. He said they gave it to him about 6 months ago. Blew off the top half of the right grip panel which ended up 20yds downrange. His hand was a little blackened, said it ached a bit. He was shooting American Eagle FMJ. The slide was stuck slightly to the rear. I don't know what caused it but I do know it sure scared the sh*t out of all of us.

It probably was a round fired with something stuck in the barrel.  The barrel bulges out beneath the slide and jams the whole thing up pretty tight with the slide only a tiny bit back.  The pressure has to go somewhere, so it finally bursts the brass case and vents down the feed ramp and into the grip area.  Sometimes the mag will blow out the bottom, but Sig mags are a strong design and pretty well asembled, so the plastic grip panel let loose.  More than likely the panel already had a fracture that weakened it and it failed along that.

Ross

My dad was watching him and the two previous shots put holes in the paper... perhaps the previous bullet broke up? Or there was an incredible amount of fouling in the barrel? I'm going to ask next week and see if they know what happened. I read somewhere that Sigs were engineered to blow out a grip in an event such as this, to avoid an unknown reaction. I know this kind of failure isn't the norm for Sigs, which made it even stranger.

There has been a rash of problems with American Eagle lately. Do a search on the web and see what you find. In fact, I think that there was a warning about AE just recently.

Glock Kb!

I would lay odds it was the AE ammo. The reloading forum has several posts about not reloading AE .223/5.56 brass due to its thinness and lack of strength.

I have put tons of crappy reloads (mine) and NEVER had a problem like that with a p220. But then again never had a bullet stuck in the barrel with another coming right behind it either. I cant think it was that fouled. I would like to see the barrel.
If ya find out i would like to hear the details