I would say it would almost have to be a double charge. Hard to tell from your pic but it looks like the cylinder split and blew the top strap off. I've seen squibs in a barrel and no harm done to the cylinder. As for +P in a non +P gun I've always heard, and most of what I have heard was from this board, that +P was safe in any 38 S&W that was model marked.

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