(The longest 'hang-fire' I've ever experienced (with a firearm) has been a couple of seconds - with some very old and horrible .38 S&W that I assume had been badly stored.)
I have had some boxes of 1954 vintage .38 S&W, some did hang, others only had a primer but no powder. After ten shots I ended up running them through the bullet puller and powder mill. Even a .22 rimfire can be unstable and go off 4/5th of the way in the barrel. I still have it as a example. What happened to the two in the tank is awefull , mistakes were made and high prices paid.