A friend had just tightened the muzzle booster on his M1919A4 using the GI cup-type wrench that fits fully over the entire booster nozzle, and got impatient and grabbed the trigger before placing his brain back into gear. Absolutely fragged the booster wrench into pieces with a ball round into it and sent all manner of pieces in every direction.
He got the larger amount of damages with several perforations into his extremities and face, nothing severe enough to warrant a hospital stay but they were cleaning it out of him for quite awhile, kind of left him loooking like he took a load of bird-shot to his front. He still says he gets small pieces working themselves out to this day and that was back in 2001.
-TomH