Another buldger of barrels is a paper case that separates from the brass. Firing paper cases over three times is a general danger. Examine potential cases for a burn line both case length wise and around the attachment to the brass.
Plastic shotshell hulls will also separate from the brass (or, in some cases, the plastic will split and result in a tear around the circumference). Most of the time, if you're paying attention, you know this immediately with a break open gun, because it will eject (or you will remove, if it's not an ejector gun) only what remains of the hull. Maybe just the brass; maybe the brass with only a short section of the plastic. In any case, at that point you need to take a good look down the bore and make sure that the missing section of the hull isn't lodged in the barrel. Usually happens with hulls that have been reloaded many times . . . but not always. I've always thought about guys shooting autos or pumps, who may not realize that what was ejected was only part of the hull. Very possibly big trouble the next time they pull the trigger.
