Over the years I've run >1,000 shooters through an "Intro to flintlocks" class. Worst injury--the only one, IIRC--was a guy who drew his thumb across a fresh flint to see how sharp it was. That took a Band-Ade to fix.
Years ago--I think I was 12 or 13 years old--I arrived at the gathering point for a parade for the centennial parade at a local village, passing an ambulance on the way in. One of the marchers had been "injured in an accidental shooting". I got some coffee and a doughnut, and sat down on the ground to wait to see if we would be marching. When I set my cup down, it tipped over: turned out I set it on the guy's detached thumb.
IIRC, I've been present twice when nipples blew out of caplocks (no injuries to the shooter). At one match, the shooter on my left had the drum break off his caplock when he fired. No injuries, but he and I were both done shooting for the day.
Saw a guy manage to ignite his powder horn when he touched off his flintlock (spout plug attached to the horn, he forgot to replace it after loading). Turned out both he and his buddy the range officer had a couple of beers for breakfast to settle their heads from the night before. Shooter had 2nd degree burns and a really nasty "rope" burn on his neck.
A couple times I've seen powder ignite when dumped down the barrel. Both shooters had burns to their hand.
Drove to a shoot in a neighboring state, got registered, and had posted my first target when I realized the RO was more-than-slightly-drunk. I immediately began packing up to leave. While I was doing that, the range officer managed to grab someone's match pistol and shoot himself in the foot. A couple of the shooters got angry when we closed the firing line, called an ambulance, etc, because they wanted to shoot "before it got hot". Two people got ambulance rides: the RO and a guy who had a suspected heart attack.
Once saw a guy split the barrel on his longrifle when he left his "ramrod" (1/2" steel rod) in the bore after loading. Barrel was 15/16"x.54 caliber. Guy lost at least one finger on his left hand.