That is unquestionably the worst example of what could happen. I am sure that was horrific and the family must be crushed. Now I am not exactly one of those flag waving drunken idiots, but I do have a cannon and every 4th of July we shoot it half a dozen times. This is an operation that is treated with respect, I have seen operators that increase the powder charge as the evening "progresses" which is a recipe for disaster. I suspect that the cannon that exploded was cast iron and shouldn't have been used at all. Mine is cast steel and another that was cast at the same time has been put through testing. The cup pressure generated by the black powder charge doesn't meet the tolerance level by even half.
I am responding one to offer my condolences and secondly to find out more specifics about how this happened in an effort to prevent other occurances.
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In the legend of King Arthur, the Fisher King was a renowned angler whose errant ways caused him to be struck dumb in the presence of the sacred chalice. I am no great fisherman, and a steelhead is not the covenant of Christ, but with each of these fish I am rendered speechless.