I saw lawsuit evidence one time, a bloody blown up gun, that blew part of a guy's face and hand off as I recall... It's no joke.
In addition to the inappropriate load issue there were some inherently bad guns sold over the years. If you're looking at a used modern-made muzzle loader Google it and look for lawsuits. In the 1970s a bunch of stuff came to market during the Bicentennial hype and not all of it was good...